SECTION II: CHAPTER 3
TECHNICAL EQUIPMENT: ON-SITE MEASUREMENTS
Contents:
- Introduction
-
Direct-Reading Instrumentation
-
Chemical Warfare Agent Detection
- Biological Agent Detection
-
Radiation Monitors and Meters
-
Air Velocity Monitors/Indoor Air Quality (IAQ) Assessment Instrumentation
- Noise Monitors and Meters
- Vibration Monitors
- Electronic Test Equipment
-
Heat Stress Instrumentation
Appendix II: 3–1. Batteries
Appendix II: 3–2. Availability, Calibration, Maintenance and Repair of Equipment: Cincinnati Technical Center (CTC)
Appendix II: 3–3. Instrument Chart
- Introduction
The purpose of this chapter is to provide a broad overview of the types of
equipment and instrumentation available for use by OSHA personnel. This
information is not a comprehensive resource for specific types of
instrumentation, nor is it intended to replace the owner’s manual. Rather, its
purpose is to provide a broad understanding of the principle of operation for
the particular type of equipment and an understanding of the capabilities and
limitations of the equipment. End users should always follow the owner's
manual and manufacturer recommendations regarding the specific operation and
maintenance of the equipment being used.
- Direct-Reading Instrumentation
Direct–reading instruments (sometimes termed real-time instruments) provide
information at the time of sampling, thus enabling rapid decision-making.
These instruments can often provide the trained and experienced user the
capability to determine if site personnel are exposed to concentrations which
exceed instantaneous (ceiling or peak) exposure limits for specific hazardous
materials. Direct-reading monitors can be useful in identifying
oxygen-deficient or oxygen-enriched atmospheres, immediately dangerous to life
or health (IDLH) conditions, elevated levels of airborne contaminants,
flammable atmospheres, and radioactive hazards. Periodic monitoring of
airborne levels with a real-time monitor is often critical, especially before
and during new work activities. Data obtained from direct-reading monitors can
be used to evaluate existing health and/or safety programs and to assure
proper selection of personnel protective equipment (PPE), engineering controls
and work practices.
The following general considerations apply to instrumentation which might be
used in potentially explosive atmospheres or in atmospheres which may contain
highly toxic airborne chemicals (as defined by 29 CFR 1910.1200 App. A and
noted below) and/or carcinogenic chemicals that may have contaminated surfaces
or may be found in airborne concentrations:
- Instruments shall not be used in atmospheres where the potential for
explosion exists (see 29 CFR 1910.307) unless the instrument is listed by a
Nationally Recognized Testing Laboratory (see 29 CFR 1910.7) for use in the
type of atmosphere present. Check the class and division ratings prior to use.
When batteries are being replaced, use only the type of battery specified on
the safety approval label. Do not assume that an instrument is intrinsically
safe. If uncertain, verify by contacting the instrument's manufacturer or the
Cincinnati Technical Center (CTC).
- For atmospheres containing carcinogens or highly toxic chemicals, a plastic
bag should be used to cover equipment to limit contamination. Ensure that the
plastic bag is not tightly sealed as this can cause back pressure on the pump.
Properly decontaminate all equipment to minimize potential contamination of
persons or objects when sampling is complete. To the extent possible, gross
decontamination should be performed after use on-site.
NOTE: Definition of Highly Toxic from Appendix A of 1910.1200
"Highly toxic:" A chemical falling within any of the following categories:
(a) A chemical that has a median lethal dose (LD50) of 50 milligrams or less
per kilogram of body weight when administered orally to albino rats weighing
between 200 and 300 grams each.
(b) A chemical that has a median lethal dose (LD50) of 200 milligrams or less
per kilogram of body weight when administered by continuous contact for 24
hours (or less if death occurs within 24 hours) with the bare skin of albino
rabbits weighing between two and three kilograms each.
(c) A chemical that has a median lethal concentration (LC50) in air of 200
parts per million (ppm) by volume or less of gas or vapor, or 2 milligrams per
liter or less of mist, fume, or dust, when administered by continuous
inhalation for one hour (or less if death occurs within one hour) to albino
rats weighing between 200 and 300 grams each.
A. Photoionization Meters
Application and Principle of Operation:
Photoionization detectors (PIDs) use a high energy ultraviolet (UV) light
source to ionize chemicals in an air stream. The charged molecules are
collected on a charged surface which generates a current which is directly
proportional to the concentration of the chemical in the air being sampled.
The ability of a chemical to be ionized is a function of its ionization
potential (IP). If the energy of the UV lamp is greater than or equal to the
IP of the chemical being sampled, then the chemical will be detected.
Typically, PID detectors will come equipped with a UV lamp at 10–10.6 electron
volts (eV). Tables listing the IP for chemicals and their relative sensitivity
are generally available from the manufacturer. Higher energy lamps (11.7 eV
for the Photovac Model 2020Pro) are available to detect chemicals which have
high IPs. For example, methylene chloride requires use of the 11.7 eV lamp for
detection because the IP for methylene chloride is 11.35 eV. In general, these
higher energy lamps have a much shorter lifetime than the 10.6 eV lamps.
In general, aromatic hydrocarbons such as benzene, toluene and xylene provide
a sensitivity of approximately 0.1 ppm with photoionization detection.
Unsaturated hydrocarbons, alcohols, ethers, and chlorinated hydrocarbons have
intermediate sensitivity by PID, and saturated hydrocarbons such as n-hexane
tend to be the least sensitive. For example, n-hexane is approximately 1/10 as
sensitive as benzene by PID. While it might be expected that the sensitivity
of a chemical would be related to its IP, this is not always the case. For
example, benzene with an IP of 9.245 eV, and which has a relatively high
sensitivity by photoionization detection, is actually slightly less sensitive
than vinyl bromide with an IP of 9.80 eV.
Calibration:
In many instances a reference gas is used to calibrate the PID. Frequently,
isobutylene gas in air is used as a calibration gas. The meter can then be
used to read directly in isobutylene units. If gases other than isobutylene
are measured, the isobutylene units can be converted using the appropriate
response obtained from the instrument manual for the PID meter used. For
example, if the response factor listed in the manual for benzene (relative to
isobutylene) is 0.5 and if a meter which had been calibrated with isobutylene
was used to measure benzene, the actual benzene concentration in air will be
one half of the meter reading. Thus, if the meter reads 5.8 ppm isobutylene in
a benzene atmosphere, the benzene concentration is actually 2.9 ppm.
Similarly, if the meter reads 10 ppm isobutylene in an atmosphere of ethyl
acetate, the ethyl acetate concentration is 38 ppm because the response factor
for ethyl acetate is 3.8.
Many PID meters are programmed with internal response factors based upon
isobutylene gas and the instrument can be set up to read ppm for the gas of
interest. Direct calibration of the instrument, or verification of the
calibration if stored response factors are used to calibrate the instrument,
is desirable. This can be done by testing a known concentration of an
atmosphere containing the chemical of interest prepared in a gas bag.
Special Considerations:
Photoionization sensitivity is dependent upon the age of the lamp and
cleanliness of the lamp window. Over time, the output of the lamp will be
reduced and also the accumulation of organic deposits on the surface of the
lamp will reduce sensitivity. A buildup of film on the lamp will reduce the
sensitivity of the meter. The meter also has a reduced sensitivity in high
humidity. One manufacturer (RAE Systems) reports up to a 30% reduction in
response for measurements in high humidity air when compared to calibration of
the same chemical in dry air. For the most accurate results, it is best to
calibrate the meter using representative air.
MicroRAE also reports that a "quenching effect" can be observed in which the
UV lamp light rays are scattered by the presence of non-ionizable gas
molecules. Water vapor, carbon dioxide, methane, and carbon monoxide can all
produce a low reading for the gas of interest if present in the air being
sampled.
Maintenance:
Follow the manufacturer's recommendations for maintaining the detector in
optimal condition. This will include routine cleaning of the UV lamp and
frequent replacement of the dust filter. Because of the fragile nature of the
lithium fluoride window on the 11.7 eV lamps, special precautions must be
followed and cleaning should only be done using Freon or chlorinated solvents.
The exterior of the instrument can be wiped clean with a damp cloth and mild
detergent, if necessary. Keep the cloth away from the sample inlet and do not
attempt to clean the instrument while it is connected to a power source.
B. Infrared Analyzers
Application and Principle of Operation:
Infrared (IR) analyzers are useful for measuring a broad range of inorganic
and organic chemicals in air. Depending upon the chemical, the sensitivity of
IR analyzers can be sufficient for industrial hygiene purposes. Because most
chemicals absorb IR light, an infrared analyzer may not be selective unless
the chemical of interest can be measured at a wavelength which is unique for
that chemical in the air sample, or the industrial hygienist is able to
determine that other interfering chemicals are not present in the work
environment. Some of the routine applications for IR analyzers include
measuring carbon dioxide in indoor air quality (IAQ) assessments; anesthetic
gases, including, nitrous oxide, halothane, enflurane, penthrane, and
isoflurane; ethylene oxide; and fumigants, including ethylene dibromide,
chloropicrin, and methyl bromide.
IR analyzers emit an infrared light which is generated from a heated metal
source. The infrared portion of the electromagnetic spectrum typically used in
infrared analysis ranges from the far infrared region at 400 cm-1 (25
micrometers) to the near infrared region 4000 cm-1 (2.5 micrometers). The
amount of infrared light that a chemical absorbs varies with the particular
wavelength of light to which it is exposed. For example, acetone, which is a
ketone, has a strong, broad absorption band around 1720 cm-1, whereas
alcohols have a strong, sharp absorbance band at approximately 3610–3670 cm-1. Because the absorbance of infrared light by a chemical changes with the
wavelength of incident light, an absorption pattern, or unique spectrum for
the chemical, can be produced by measuring the absorbance of the incident
light for a chemical over the 400–4000 cm-1 infrared range. This infrared
absorbance spectrum can be compared to a library of known chemicals for
identification purposes.
For measuring the amount of a chemical in air, a wavelength is selected for
which the chemical of interest absorbs the light. The amount of light absorbed
by the air sample at this wavelength would be proportional to the amount of
the chemical in the sample if there is no other chemical present in the air
which absorbs at that same wavelength. In some instances, a weaker absorbance
band at a different wavelength is chosen to measure a chemical in air, if that
alternate wavelength is uniquely absorbed by that chemical of interest. The
selected wavelength for analysis of a chemical is chosen both because the
chemical of interest has sufficient absorbance at that wavelength and
sufficient specificity to exclude the absorbance of other chemicals. For
example, acetone in air absorbs IR at both 8.4 and 11.0 microns. If methyl
acrylate was also known to be present in the air, the 11.0 micron IR
wavelength would be selected because methyl acrylate absorbs at 8.4 microns.
The sensitivity of IR detection can also be varied by changing the path length
through which the light source passes. This is accomplished by internally
mounted mirrors within the analyzer which can vary the path length for the
light source for the Miran 205B analyzer from 0.5 meters to 12.5 meters.
Calibration:
The Miran 205B analyzer is pre-calibrated for a list of chemicals which are
stored in the instrument library. A sampling loop kit which recirculates a
known volume of air is available for the instrument which allows the injection
of a known amount of a volatile liquid or gas into the IR sampling cell. In
this fashion, the instrument's pre-calibration can be verified prior to and
after its use. Instrument zeroing is performed by using a charcoal filter
attachment to remove chemicals from the air.
Special Considerations:
Infrared analyzers may not be specific for the chemical of interest because
other chemicals present in the work environment air may also absorb at the
same wavelength. Cell window degradation will occur if the analyzer is used in
the presence of ammonia and many alkyl amines, such as methyl amine.
Maintenance:
Field maintenance is limited to replacement of the zeroing filter after 30
uses and replacement of the particulate filter in situations where adsorbed
particulates or non-volatile liquids may have contaminated the filter surface.
Field calibration is conducted according to the manufacturer's
recommendations.
Gas, Oxygen and Explosibility (Combustible Gas) Monitors
C. Gas Monitors
Application and Principle of Operation:
This monitor uses an electrochemical voltammetric sensor or polarographic cell
to provide continuous analyses and electronic recording. In operation, sample
gas is drawn through the sensor and absorbed on an electrocatalytic sensing
electrode after passing through a diffusion medium. An electrochemical
reaction generates an electric current directly proportional to the gas
concentration. The sample concentration is displayed directly in parts per
million, % oxygen or % LEL (lower explosive limit). Since the method of
analysis is not absolute, prior calibration against a known standard is
required. Tests have shown the method to be linear; thus, calibration at a
single concentration, along with checking the zero point, is sufficient. The
oxygen meter displays the concentration of oxygen in percent by volume
measured with a galvanic cell. Other electrochemical sensors are available to
measure carbon monoxide, hydrogen sulfide, and other gases. Some units have an
audible and/or visual alarm that warns of low oxygen levels, LEL or
malfunction. These pieces of equipment generally rely on the passive diffusion
of air into the detector, however, some applications will require the user to
attach a mechanical pump to actively draw air into the sensor.
Calibration:
Calibrate the direct-reading gas monitor with the appropriate calibration
(span) gases before and after each use in accordance with the manufacturer's
instructions. The monitor should be calibrated at the altitude at which it
will be used. Changes in total atmospheric pressure caused by changes in
altitude will influence the instrument's response. The unit's instruction
manual provides additional details on the calibration of sensors.
Special Considerations:
Interference from other gases can be a problem (see manufacturer's
literature).
If the span gas is directly fed into the instrument from a pressurized
cylinder equipped with a regulator, the pump must be disconnected from the
sensor to avoid sensor damage and the span gas flow rate should be set to
match the sampling rate of the pump.
D. Oxygen Monitors
Application and Principle of Operation:
Oxygen measurements are usually made along with combustible gas measurements
for confined spaces. Oxygen meters typically use galvanic electrochemical
cells (sensors). The generated current in the sensor, which is produced from
an oxidation reaction, is directly proportional to the rate of oxygen
diffusion into the cell. Most meters are calibrated to measure oxygen
concentrations between 0 and 25% by volume in air. Normal air contains about
20.9% oxygen. Meter alarms are usually set to indicate an oxygen-deficient
atmosphere at concentrations lower than 19.5% and an oxygen-rich atmosphere at
concentrations greater than 23.5%.
Calibration:
Calibration is typically accomplished using fresh outdoor air (20.9% oxygen).
Calibrate immediately before testing at or near the temperature of the tested
atmosphere.
Maintenance:
Oxygen sensors are inherently self-consuming and generally last from 6 to 12
months. Some sensors can be reactivated by returning them to the manufacturer,
but in most cases, an exhausted sensor is discarded and replaced with a new
one.
E. Explosibility (Combustible Gas) Monitors
Application and Principle of Operation:
These meters use elements which are made of various materials such as platinum
or palladium as an oxidizing catalyst. The element is one leg of a Wheatstone
bridge circuit. These meters measure gas concentration as a percentage of the
lower explosive limit of the calibrated gas.
Calibration:
Before using the monitor each day, calibrate it with a known concentration of
appropriate combustible gas (usually methane in air) equivalent to 25-50% LEL
full-scale concentration. Follow manufacturer's instructions.
Special Considerations:
Silicone compound vapors and sulfur compounds will cause desensitization of
the combustible sensor and produce erroneous (low) readings.
High relative humidity (90%-100%) causes hydroxylation, which reduces
sensitivity and causes erratic behavior including inability to calibrate.
Oxygen-deficiency or enrichment such as in steam or inert atmospheres will
cause erroneous readings for combustible gases.
In drying ovens or unusually hot locations, solvent vapors with high boiling
points may condense in the sampling lines and produce erroneous (low)
readings.
High concentrations of chlorinated hydrocarbons such as trichloroethylene or
acid gases such as sulfur dioxide will depress the meter reading in the
presence of a high concentration of combustible gas.
High molecular weight alcohols can burn out the meter's filaments.
For gases and vapors other than those for which a device was calibrated, users
should consult the manufacturer's instructions and correction curves.
Maintenance:
The instrument requires no short-term maintenance other than regular
calibration and recharging of batteries. Use a soft cloth to wipe dirt, oil,
moisture, or foreign material from the instrument.
F. Detector Tubes
Application and Principle of Operation:
Detector tubes and their associated pumps are portable equipment capable of
measuring concentrations of a large number of gases and vapors present in
industrial atmospheres. Detector tubes of a given brand are to be used only
with a pump of the same brand. A brand of tubes is calibrated specifically for
the same brand of pump and may give erroneous results if used with a pump of
another brand. Always review the manufacturer’s recommendations and guidance
for chemical–specific detector tubes.
Detector tube pumps can be hand-held during operation (weight: 8-11 ounces),
or they can be an automatic type (weight: about 4 pounds) that samples using a
preset number of pump strokes. A full pump stroke for either type of
short-term pump has a volume of about 100 mL.
There is a wide variety of commercially available detector tubes. Their
operation consists of using a pump to draw a known volume of air through a
detector tube designed to measure the concentration of the substance of
interest. The concentration is usually determined by the colorimetric change
of an indicator which is present in the tube contents.
Detector tubes are sealed glass tubes filled with an appropriate indicator
chemical to react with a particular gas or vapor and give a color reaction. To
make a determination, the seals are broken at each end of the tube and a
specific volume of the air being sampled is drawn through by a hand-operated
or mechanical pump. Each tube is formulated with a specific reagent (indicator
chemical) that absorbs and reacts with the gas or vapor being measured,
causing a colorimetric stain. Many of the tubes that are manufactured are of
the direct– reading type. In this type, the colorimetric stain varies in
length proportionally to the concentration of gas or vapor being measured. The
concentration of gas/vapor is read directly off a scale on the side of each
tube. There are also chart comparison tubes that work similarly to the
direct–reading type. After a sample is taken, the stain length is compared to
a printed concentration chart enclosed with each box of tubes. A third type of
tube is the color comparison type. In this type, the intensity of color
change, rather than the length of stain, is compared to a standard color
chart. In addition to these tubes, which give an immediate reaction, long
duration tubes for monitoring various toxic gases or vapors throughout the
normal workday are available. These tubes can be worn by the employee in a
special holder, while a portable lightweight pump continuously draws a
measured volume of air through the tube. At the end of the shift, the tube can
be evaluated to give a time-weighted average (TWA) exposure for the working
day.
It is important that the sampler be aware of the specific manufacturer's
direct–reading instrument's degree of precision and be able to report the
data's degree of accuracy for a particular measurement technique. For
instance, many detector tubes have a degree of precision that ranges from +/-
25% to 35% of the colorimetric change reaction within the detector tube.
Calibration:
Calibrate the detector tube pump for proper volume measurement at least
quarterly. Simply connect the pump directly to an inverted buret with a
detector tube in-line. Use only detector tubes and pumps from the same
manufacturer.
Wet the inside of the 100-mL buret with soap solution. For volume calibration,
experiment to get the soap bubble even with the zero (0) mL mark of the buret.
For piston-type pumps, pull the pump handle all the way out (full pump stroke)
and note where the soap bubble stops; for bellows-type pumps, compress the
bellows fully; for automatic pumps, program the pump to take a full pump
stroke. For either type pump, the bubble should stop between the 95-mL and
105-mL marks. Allow up to 4 minutes for the pump to draw the full amount of
air. The time interval varies with the type of detector tube being used
in-line with the calibration setup.
Also check the volume for 50-mL (one-half pump stroke) and 25-mL (one-quarter
pump stroke) if applicable. Permissible error is ± 5%. If the error is greater
than ± 5%, send the pump to the CTC for repair and recalibration. Record the
calibration information required on the Calibration Log (OSHA-93).
Each day and prior to use, perform a pump leakage test by inserting an
unopened detector tube into the pump and attempt to draw in 100 mL of air.
After a few minutes, check for pump leakage by examining the pump compression
for bellows-type pumps or return to resting position for piston-type pumps.
Automatic pumps should be tested according to the manufacturer's instructions.
In the event of leakage that cannot be repaired in the field, send the pump to
the CTC for repair. Record that the leakage test was performed on the
Direct-Reading Data Form (OSHA-93).
Brand-Specific Instructions
DRAEGER, MODEL 31 (BELLOWS):
When checking the pump for leaks with an unopened tube, the bellows should not
be completely expanded after 10 minutes. For the DRAEGER ACCURO PUMP
(BELLOWS), a 15-minute period is used and the end-of-stroke indicator should
not be noticeable after this period.
DRAEGER, QUANTIMETER 1000, MODEL 1 (AUTOMATIC):
A battery pack is an integral part of this pump. The pack must be charged
prior to initial use. One charge is good for 1,000 pump strokes. During
extended use periods, it should be recharged daily. If a "U" (under voltage)
message is continuously displayed in the readout window of this pump, the
battery pack should be immediately recharged. A leak test is performed by
turning the system on, setting the pump stroke indicator to "2" or greater,
inserting an unopened tube into the holder and pressing the start/stop key.
When the second stroke has not started after 30 minutes, the device is
considered sufficiently gas-tight.
MATHESON-KITAGAWA, MODEL 8014-400A (PISTON):
When checking the pump for leaks with an unopened tube, the pump handle should
be pulled back to the 100-mL mark and locked. After 2 minutes, the handle
should be released carefully. It should return to zero or resting position.
After taking 100-200 samples, the pump should be cleaned and relubricated.
This involves removing the piston from the cylinder, removing the inlet and
pressure-relief valve from the front end of the pump, cleaning, and
relubricating.
MINE SAFETY APPLIANCES, SAMPLAIR PUMP, MODEL A, PART NO. 46399 (PISTON):
The pump contains a flow-rate control orifice protected by a plastic filter
which periodically needs to be cleaned or replaced. To check the flow rate,
the pump is connected to a buret and the piston is withdrawn to the 100-mL
position with no tube in the tube holder. After 24-26 seconds, 80 mL of air
should be admitted to the pump. Every 6 months the piston should be
relubricated with the oil provided.
MINE SAFETY APPLIANCES KWIK DRAW™ SAMPLING PUMP, PART NO. 487500 (BELLOWS):
The pump contains a filter disk that needs periodic cleaning or replacement.
The bellows shaft can be cleaned and lubricated with automotive wax if
operation becomes jerky. This pump is tested for leakage by inserting an
unopened tube into the holder, deflating the pump fully and releasing. After
10 minutes the distance of the bellows to the frame should be ½ inch or
greater.
GASTEC MODEL GV-100 PISTON SAMPLING PUMP:
When checking the pump for leaks, first confirm that the inlet clamping nut is
firmly tightened. Next, push the pump’s handle fully in and align the guide
marks on the pump shaft and handle. Then insert a fresh unbroken tube into the
rubber inlet of the pump. Pull out the handle fully until it is locked, and
wait 1 minute. Unlock the handle (by turning it more than 1/4 turn) and guide
it back gradually, applying a little force. Otherwise, the handle will spring
back due to the vacuum in the cylinder and may damage the internal parts.
Confirm that the handle returns to the initial position and the guideline on
the pump shaft is not seen. If this is not confirmed, follow the maintenance
procedures explained in the operations manual for the pump, or contact the
Nextteq representative for maintenance assistance. The maintenance procedures
involve leak checks on the inlet clamping nut and rubber inlet, and performing
pump cylinder lubrication.
Special Considerations:
Detector tubes and pumps can be used to measure more than 200 organic and
inorganic gases and vapors in air. Detector tubes normally have a shelf life
of one to two years when stored at 25 °C. Expiration dates are generally
printed on the box or on each tube. In general, avoid excessively low (less
than 35°F) or high (greater than 78°F) temperatures and direct sunlight which
can adversely affect the properties of the tubes. Refrigerated storage
prolongs shelf life. Detector tubes should not be used when they are cold.
They should be kept at room temperature for about one hour prior to use.
Outdated detector tubes (i.e., beyond the printed expiration date) should not
be used unless their performance has been verified.
Several different types and brands of detector tubes have been evaluated for
screening use by the Salt Lake Technical Center (SLTC). Information regarding
these evaluations can be obtained by contacting the SLTC.
Specific manufacturer’s models of detector tubes for individual gases/vapors
are listed in OSHA’s Chemical Sampling Information files. The specific tubes
listed are designed to cover a concentration range near the PEL. Concentration
ranges are tube-dependent and can be anywhere from one-hundredth ppm to
several thousand ppm. The limits of detection depend on the particular
detector tube. Detector tube accuracy varies with tube manufacturer and with
each detector tube range as described above.
Be sure to read and follow the manufacturer’s instructions regarding
corrections that must be made to sample readings for temperature, humidity,
and pressure so that readings are valid.
A limitation of many detector tubes is the lack of specificity of the chemical
indicator. Many indicators are not highly selective and can cross-react with
other gases and vapors. Manufacturer’s manuals describe the effects of
interfering contaminants. Detector tubes generally only give
near-instantaneous measurements, thus will not reflect time-weighted average
levels of the hazardous substances present. If long-term sampling for TWA
measurements is desired, some long-term detector tubes used in conjunction
with air sampling pumps or diffusive/dosimeter tubes are available. Otherwise,
measurements may be made from gas bags that have slowly been filled at a
constant flow rate (such as from the exhaust of a sampling pump) with
workplace atmospheres.
G. Mercury Analyzer-Gold Film Analyzer
Application and Principle of Operation:
This instrument measures mercury in air by drawing an air sample over a gold
film. The Jerome Model 431X model has a reported practical detection limit of
0.01 mg/m3. The mercury adsorbed onto the gold surface changes the resistance
of current flow. The change in resistance is a function of the mass of mercury
collected on the gold film. Results can be displayed in mg/m3 of mercury or
total mass of mercury in the air sample collected. Potential interferences
which can produce a positive reading include chlorine, nitrogen dioxide,
hydrogen sulfide, high concentrations of ammonia, and most mercaptans. These
interferences are removed from the air stream ahead of the gold film by
drawing the air sample through an "acidic gas filter" which contains sodium
hydroxide and soda lime. For use in high chlorine environments, an optional
chlorine filter can be used.
Calibration:
Calibration is performed by the manufacturer on a periodic basis. Because of
the gold film/mercury interaction, the instrument should produce stable,
accurate readings without the need for frequent recalibration.
Special Considerations:
The gold film sensor becomes saturated with mercury after collecting
approximately 0.5 mg of mercury, or approximately 50 readings of 0.1 mg/m3 of
mercury. The meter then must be placed on line power and the gold film sensor
regenerated at elevated temperature. The accuracy of the readings is a
function of the temperature, so it is necessary to allow approximately 30
minutes after regeneration for the sensor to equilibrate.
The instrument readings are sensitive to temperature fluctuations. If a
significant temperature change occurs while using the meter, it will be
necessary to re-zero the meter at the new temperature.
Maintenance:
Routine maintenance includes periodic replacement of filters and regeneration
of the gold film sensor to remove mercury after use of the instrument.
H. Particle Monitors (Condensation Nuclei)
Application and Principle of Operation:
Condensation-nuclei counters are based upon a miniature, continuous-flow
condensation nucleus counters that take particles too small to be easily
detected, enlarges them to a detectable size, and counts them. Submicrometer
particles are grown with alcohol vapor as they pass through a heated saturator
lined with alcohol–soaked felt, and then condense the alcohol on the particles
in a cooled condenser. Optics focus laser light into a sensing volume.
As the droplets pass through the sensing volume, the particles scatter the
light. The light is directed onto a photodiode which generates an electrical
pulse from each droplet. The concentration of particles is counted by
determining the number of pulses generated. Applications include the testing
of respirators and real-time dust monitors.
A counter totals individual airborne particles from sources such as smoke,
dust, and exhaust fumes. Models typically operate in one of three possible
modes, each with a particular application. In the "count" mode, the counter
measures the concentration of these airborne particles. In the "test" (or fit
test) mode, measurements are taken inside and outside a respirator and a fit
factor is calculated. In the "sequential" mode, the instrument measures the
concentration on either side of a filter and calculates filter penetration.
This instrument is sensitive to particles as small as 0.02 micrometers.
However, it is non-specific to variations in size, shape, composition, and
refractive index.
Calibration:
Check the counter before and after each use in accordance with the
manufacturer's instructions. This procedure usually involves checking the zero
of the instrument. Annual calibration is handled through the CTC.
Maintenance:
Reagent-grade isopropyl alcohol for use in these types of instruments can be
obtained from the CTC Agency Expendable Supply Program.
Isopropyl alcohol must be added to the unit after 5–6 hours of operation under
normal conditions. Take care not to overfill the unit. A fully charged battery
pack will normally last for about 5 hours of operation. Low battery packs
should be charged for at least 6 hours. Battery packs should not be stored in
a discharged condition.
Storage preparation (always follow the manufacturer’s recommendations):
Dry the saturator felt by installing a freshly charged battery pack without
adding alcohol. Allow the instrument to run until the LO message (low battery)
or the E-E message (low particle count) appears. Some instruments allow you to
remove the alcohol cartridge for storage purposes.
Remove the battery pack and install the tube plugs into the ends of the
twin-tube assembly.
I. Photodetection
Application and Principle of Operation:
Photodetectors operate by detecting scattered electromagnetic radiation in the
near infrared region. Photodetectors can be used to monitor total and
respirable particulates. The device measures the concentration of airborne
particulates and aerosols including dust, fumes, smoke, fog, mist, etc.
Calibration:
Factory calibration is required.
Special Considerations:
Certain instruments have been designed to satisfy the requirements for
intrinsically safe operation in methane-air mixtures.
Maintenance:
When the photodetector is not being operated, it should be placed in its
plastic bag, which should then be closed. This will minimize the amount of
particle contamination of the inner surfaces of the sensing chamber.
After prolonged operation or exposure to particulate-laden air, the interior
walls and the two glass windows of the sensing chamber may become contaminated
with particles. Although repeated updating of the zero reference following the
manufacturer's procedure will correct errors resulting from such particle
accumulations, this contamination could affect the accuracy of the
measurements as a result of excessive spurious scattering and significant
attenuation of the radiation passing through the glass windows of the sensing
chamber.
- Chemical Warfare Agent Detection
There are several methods and types of instruments that can be used in the
detection of chemical warfare agents, such as nerve, blister, blood, and
choking agents. However, most of these agents (nerve and blister) have
extremely low occupational exposure limits, and nearly all the detection
methods lack the sensitivity required to provide results at these low levels.
It is important to understand the capabilities, uses, and limitations of each
type of detection device or instrument. The manufacturer of each system
provides clear and specific use instructions with each kit. Users should
familiarize themselves with these instructions, know the limitations of each
device or instrument, and practice the use of the kits while wearing
appropriate PPE in a non-contaminated environment. The following sections
highlight some types of equipment that are used for detection of chemical
agents. Generally, use of these detection systems will be limited to specially
trained and equipped personnel at SLTC or other specially trained and equipped
OSHA personnel. The following summarizes specialized direct reading
capabilities that OSHA has access to and should be considered informational by
all other personnel. These systems should only be used after consultation with
SLTC and under close SLTC guidance.
A. Military Detection Papers/Kits
a. M8/C8 Detector Paper
The M8 detector paper was developed to detect liquid agents, specifically V-
and G-type nerve agents, and H-type blister agents. The C8 paper is equivalent
to the M8 paper; the "C" indicates a version manufactured for commercial use.
These papers do not detect chemical agent vapors. The sheets are impregnated
with chemical compounds that change to green, yellow, or red depending on the
type of liquid agent encountered. A color chart accompanying the booklet helps
determine the type of agent detected. The result is qualitative, but the
detector paper has a sensitivity of about 20 micro liters (µL) of liquid. Some
substances can act as interferences and produce false positives, such as
insecticides, antifreeze, and petroleum products.
A similar product, termed "3-way" paper is also available. This detector paper
is equivalent to the M8/C8 papers, except that it includes an adhesive backing
that can be used to apply the paper to equipment or PPE.
b. M9 Detector Paper
The M9 paper detects the presence of liquid nerve and blister agents by
turning a reddish color. It does not distinguish the type of agent, nor does
it detect chemical agent vapors. It will detect a liquid agent droplet with a
diameter of approximately 100 micrometers (µm). Interfering substances that
will produce a false positive include petroleum products, antifreeze, and
insecticides. The papers come in a roll and are adhesive-backed.
c. M256A1 Detector Kit
The M256A1 Chemical Agent Detection Kit is designed to detect and identify
chemical agent vapors, including blood (AC & CK), blister (H, HN, HD, CX, L),
and nerve (V & G series) agents. The test consists of a series of chemical
ampoules that are broken and exposed to the air. The reagents in the ampoules
react with chemical agent vapors to produce a color change. A color chart and
instructions included with the kit are used to determine the type of agent(s)
that are present. The M256A1 is relatively sensitive, and can detect some of
the agents below the Immediately Dangerous to Life or Health (IDLH) levels.
The kit also includes booklets of M8 paper for detecting liquid agents.
d. C-2 Detector Kit
The C-2 Chemical Agent Detector Kit is used by the Canadian Military for
detecting chemical agent vapors. The C-2 kit utilizes various colorimetric
detection tubes for identifying nerve, blister, blood, and choking agents.
Similar to the M256A1 kit, it will allow detection of some agents below IDLH
levels. It also contains a booklet of M8 paper for use with detection of
liquid agents.
B. Colorimetric Tubes
Colorimetric tubes are made by several manufacturers, and their function is
essentially the same. They contain a series of tubes which can be used to
detect airborne chemical agents, as well as toxic industrial chemicals.
Conducting a single test with one or more tubes takes two to five minutes to
complete. There are some tubes, such as those for blister and nerve agents,
which give a qualitative detection of the presence of that family of chemicals
up to near IDLH levels. The industrial agents (blood agents and choking
agents) can be specifically identified and quantitatively measured in ppm to
below PEL levels. An example of colorimetric tubes designed specifically for
chemical agents is the Dräeger Civil Defense SimultestTM (CDS) Kit.
C. Portable Chemical Agent Detectors
Most types of portable, traditional chemical detection equipment, such as
photoionization detectors, flame ionization detectors, electrochemical
sensors, infrared analyzers, etc. can be used for chemical agent detection.
These types of instruments are discussed in other sections of the Technical
Manual. However, these instruments have poor sensitivity with respect to
chemical agents and cannot provide detection below IDLH levels. Some
instruments have been developed for use specifically with chemical agents, and
research is ongoing. Some of the more popular technologies and instruments are
discussed below.
a. Ion Mobility Spectrometers
An ion mobility spectrometer (IMS) operates by drawing air into the instrument
where it is ionized with a radioactive source. The ionized molecules travel
through a charged tube, where they become separated according to their mass
and mobility before reaching a collector electrode. An electronic signature is
produced for each ion, which gives an indication of the type and relative
concentration of agent present. IMS detectors are used mainly to detect nerve,
blister, and blood agents. Examples of IMS detectors include the Chemical
Agent Monitor (CAM), Improved Chemical Agent Monitor (ICAM), APD2000, and
SABRE 4000.
These instruments will not detect at levels below IDLH for most chemical
agents. They are best used for site reconnaissance, or to screen for
contamination on equipment or personnel. Some interferents that may cause
false alarms with an IMS include the following: cleaning compounds and
disinfectants that contain additives such as menthol and methyl salicylate
(oil of wintergreen); aromatic vapors, such as perfumes and food flavorings;
and exhaust from some motors and fumes from explosives and propellants.
b. Surface Acoustic Wave
Surface acoustic wave (SAW) sensors are comprised of piezoelectric crystals
with selective surface coatings. As the mass of a chemical vapor sample flows
over the sensors, it is absorbed into the surface which results in a change in
vibration frequency of the sensor. An internal microprocessor in the
instrument measures these changes, providing detection and identification of
the chemical agent. Portable instruments utilizing SAW technology are
available for detection of nerve and blister agents. Examples of SAW
instruments include the HAZMATCAD and SAW MiniCAD. As with IMS detectors, SAW
instruments will not allow detection of most chemical agents below IDLH
levels. However, SAW detectors are less susceptible to false positive alarms
from interfering substances.
D. Gas Chromatograph/Mass Spectrometer
Additional instruments that can be used for chemical agent detection and
identification are gas chromatographs (GC) and mass spectrometers (MS). These
are generally laboratory-type instruments which require skilled laboratory
technicians for operation and interpretation of results. A few have been
hardened for use in vans and portable handheld units that can be used in the
field, however, the technicians normally must collect a sample from the
suspect material and bring it to the instrument. Currently, the GC or GC/MS is
the only instrument that can verify the concentrations of nerve agents down to
occupational TWA levels (PEL/TLV). This is important for applications where it
is important in determining the appropriate types and levels of PPE or to
verify that decontamination is complete.
An example of a portable GC is the MINICAMS. This instrument is used
extensively in Department of Defense depots where chemical agents are stored
and used by other agencies in the field. The MINICAMS can provide automatic,
quantitative identification of the chemical agents for which it was
calibrated.
E. Health Response Team (HRT) Availability
The following equipment is maintained by the HRT for use in chemical agent
detection:
a. Military Detection Papers/Kits: M8/C8 paper, M9 paper, M256A1 kits, and C-2
kits.
b. APD2000; 2 IMS detection units as described above. Each OSHA region is also
equipped with a single APD2000 unit.
NOTE: The Health Response Team (HRT) also serves as the coordinator for OSHA's
Chemical Specialized Response Team (SRT) and can provide additional assistance
and technical information regarding chemical warfare agent detection. Special
precautions are also necessary to prevent exposure when working with chemical
warfare agents, such as PPE and/or other work practices. Contact the HRT for
more details.
- Biological Agent Detection
Sampling and analysis for biological agents is a rapidly growing field. Many
techniques and technologies are still under development. There are various
factors to consider when sampling for biological agents, such as: method of
dispersion for the agent, purpose of the sampling (e.g., to identify the
agent, determine extent of contamination, confirm decontamination, etc.),
environmental conditions, persistence of the agent, physical state of the
agent, area/volume to be sampled, laboratory protocols, and others. It is
important to note that biological agents (bacteria, viruses, toxins) are
particulates, and therefore, methods are designed for particulate sampling.
The following sections highlight some types of equipment that may be used for
sampling and detection of biological agents.
A. Surface/Bulk Sampling
a. Swabs
Swabs have been used frequently when sampling surface areas for the presence
of biological agents. Swab tips come in a variety of materials, such as
cotton, DacronTM, polyester, rayon, and foam. Shafts can be comprised of either
wood or plastic. Generally, synthetic swab tips with plastic shafts are
recommended because they are not of biological origin and will not interfere
with DNA-based detection systems. Swabs may be used dry or wetted with a
buffer solution. In general, studies have shown that wet swabs have higher
collection efficiency than dry swabs.
b. Wipes and Sponges
Wipes and sponges are often used because they can sample larger surface areas
and have a higher collection efficiency compared to swabs. They can also be
used in a dry or wet fashion. Various styles and materials for wipes and
sponges are available. As with swabs, synthetic materials are recommended to
eliminate potential interference problems with detection systems.
c. Vacuum Methods
Vacuum methods can be used when it is necessary to sample very large surface
areas or areas that are porous, and it is impractical to use swabs or wipes.
They are also useful to gather bulk dust samples for analysis. One method
utilizes a high efficiency particulate air (HEPA) vacuum equipped with a dust
collection filter sock which is used to capture the sample. Large surface
areas can be vacuumed, and the dust gathered in the sock is then analyzed for
the presence of biological agents. A similar method uses a portable sampling
pump equipped with a filter cassette to "vacuum" particulates from smaller
areas, and at lower flow rates. The filter can then be analyzed for biological
agents.
d. Agar Plates
Agar plates, also known as "sticky plates", can be used to sample a surface by
contacting the plate directly to the surface. The particulates from the
surface will adhere to the plate, which can then be analyzed by culture to
identify any biological agents. This method has been used by various agencies
during investigations of incidents involving biological agents.
B. Air Sampling
Air sampling can be performed to determine the presence of airborne biological
particulates. Essentially, a volume of air is drawn through a filter or
deposited in another medium, and the captured particulates are then analyzed
to identify biological agents. High flow rates are generally desirable, since
this allows higher sample volumes and increases the likelihood of detecting
the suspect agents. However, it should be noted that some organisms are
fragile, and the high velocities and impact mechanisms may kill the organism
during the sampling process.
Low-flow air sampling methods consist of traditional personal sampling pumps
equipped with capture devices such as filter media or liquid impingers. These
low-flow methods have the advantage of being small and portable; however, due
to their low sample volume they will have a relatively high limit of
detection.
Impactors, such as the Andersen Sampler, utilize higher flow rates (around 30
L/min), sample a greater air volume, and, therefore, increase the likelihood
of detecting the agent. The Andersen Sampler and similar types of impactors
capture the particulate directly on an agar plate which can then be analyzed
in a laboratory by culture method.
High volume area samplers are also available for biological agents. These
samplers possess flow rates ranging from 200 to 600 L/min, so they are able to
sample very large volumes of air. Some instruments deposit the particulate on
a filter, while others capture it in a liquid solution.
C. Generic Detection
There are several techniques and instruments available that will allow
responders to perform a generic detection for biological agents. These methods
will not identify a specific agent, but can be used to determine if a suspect
material is of biological origin, and to rule out hoax materials. The
following are some examples of equipment types:
a. Particle Analyzers: The particle size of a sample can be analyzed and
compared to known size ranges for biological materials. If the particle size
is too large or too small, biological materials can be ruled out.
b. Fluorometer: These instruments will detect the presence of DNA, which is a
component of most biological materials. A positive response by the meter for a
given sample indicates a biological material, but again, does not identify the
material or agent.
c. Luminometer: A luminometer operates similarly to a fluorometer, except that
it will detect the presence of adenosine triphosphate (ATP) in a sample. ATP
is another component of a cellular organism, thereby indicating a biological
material.
d. Colorimeter: Colorimeters can be used to detect protein from a sample.
Again, protein is present in biological organisms, so these instruments can
indicate if the material is biological in origin.
e. Protein Paper: Similar to a colorimeter, these paper strips can indicate if
a given sample contains protein, and is, therefore, biological.
f. pH Paper: The pH of a sample is tested with pH paper strips; if the pH
range is between 5 and 9, the material may be biological. If the pH is outside
this range (below 5 or above 9), then biological materials can be ruled out.
D. Identification
a. Immunoassay/Handheld Assay
An immunoassay test, also known as a handheld assay (HHA), can be performed on
an obtained sample to identify a specific agent. These HHA tests rely on an
antigen/antibody reaction to identify the suspect agent. The test is
presumptive, meaning that a given agent must be suspected and then tested with
its specific HHA for confirmation. For example, if B. anthracis (anthrax) is
suspected, the sample is tested using an HHA designed for B. anthracis; a
positive result confirms the presence of the organism while a negative result
indicates that the sample does not contain that specific organism. The HHA
units are small, the test can be performed in the field, and they rely on a
visual colorimetric change for sample results. Some HHA systems come with an
electronic reader to aid in detecting the colorimetric change.
HHAs are under scrutiny due to limitations on sensitivity and specificity, and
high false negative and false positive rates. The results from an HHA test
should not be relied upon alone and further confirmatory analysis should
always be performed. However, these tests are used widely by first responders
as a rapid field test. Although they are presumptive, their results can assist
decision makers in taking protective actions, treating potential infections,
and involving other authorities as necessary.
b. Polymerase Chain Reaction
Polymerase chain reaction (PCR) is a system that allows identification of an
agent based on its DNA. The DNA from the sample is obtained and reproduced
rapidly to produce a quantity that is detectable by the instrumentation. For
example, after thirty cycles with the PCR system, one copy of DNA from an
agent sample can be reproduced until there are one billion copies, which can
then be analyzed and identified.
PCR is performed real-time through detection by fluorescence. During the PCR
cycle, DNA-specific "probes" with fluorescent dyes are attached to the DNA
sample which allows detection. PCR can be performed in a laboratory, or in the
field with semi-portable instrumentation. Specific reagents and supplies are
necessary to perform the analysis.
PCR has been useful for biological agent detection since it has excellent
sensitivity, good specificity, and provides real-time results. Some weaknesses
of PCR to consider are the following: potential interferences from other
substances in the sample, reagent stability, and sample viability, since PCR
will detect the presence of both live and dead organisms, but will not
distinguish between the two.
c. Culture
Analysis by culture is considered by many to be the "gold standard" for the
analysis of biological agents. Samples are sent to a laboratory where they are
prepared and applied to an agar plate on which the suspect biological
organisms are allowed to grow. After a sufficient period of time (usually 24
hours or more), visible growth can be examined to detect the presence of the
biological agent(s). Often, culture is used for the confirmatory analysis of
previous detection methods for a given sample (HHAs, PCR). Some disadvantages
of culture include delayed results and the procedure will only detect living
organisms. Any biological agent that has died before the analysis has begun
will not be detected.
HRT Availability:
The following equipment is maintained by the HRT for use in biological agent
sampling and analysis:
a. Handheld Assays for the following agents: anthrax, plague, brucellosis,
tularemia, Venezuelan equine encephalitis, staphylococcal enterotoxin B,
botulinum toxin, ricin, smallpox, and Q fever.
b. HEPA Vacuums: Two units with filter socks and other supplies specifically
for use with biological agent sampling.
c. Andersen Samplers: Two units.
d. Dry Filter Units (DFU): Two units. The DFU is a high-volume air sampler
designed for biological agent sampling. It operates at flow rates up to 600
L/min and utilizes a filter pad for capturing the agent.
e. Surface/Bulk Sampling: Various wipe, sponge, and swab sampling kits.
NOTE: The HRT also serves as the coordinator for OSHA's Biological SRT and can
provide additional assistance and technical information regarding biological
agent detection. Special precautions such as PPE and/or other work practices
are also necessary to prevent exposure when working with biological agents.
This information is provided as a reference for specially trained personnel
and is not generally intended for CSHO use. Contact the HRT for more details.
- Radiation Monitors and Meters
IONIZING RADIATION
The following sections contain a brief description of the types of instruments
that may be used for monitoring exposures to ionizing radiation and
radioactive materials.
A. Survey Meters
Application and Principle of Operation:
Radiation survey meters are used to locate and quantify sources of ionizing
radiation or to quantify the exposure rate from sources of ionizing radiation.
To assess the quantity of radioactive materials present, survey meters are
typically calibrated to measure counts per minute (cpm). To measure the
exposure rate from radiation sources, survey meters are calibrated to measure
roentgens per hours (R/h). Most survey meters have either gas filled detectors
or scintillation detectors. Not all survey meters are configured to measure
all radiation types. Survey meters must be chosen based on the type and energy
of the radiation you expect to measure and whether you wish to measure cpm or
R/h.
Calibration:
Calibration is performed by the manufacturer on a periodic (usually annual)
basis.
HRT Availability:
a. Ludlum Model 3 with 44-9 Pancake GM Detector
The Ludlum Model 3 is a general purpose survey meter fitted with a pancake
Geiger Mueller (GM) detector capable of measuring α, β, γ, and X radiations.
This instrument will measure count rates over a range of 0–500,000 cpm.
b. Ludlum Model 2360 with 43-93 Alpha/Beta Scintillator
The Ludlum Model 2360 is a survey meter capable of measuring and
discriminating between α and β radiations. It is fitted with a Ludlum 43-93
alpha/beta scintillation detector. The meter will measure count rates over a
range of 0–500,000 cpm.
c. Ludlum Model 192 MicroRTM Meter
The Ludlum Model 192 is a low-level (μR/h) γ- and X-radiation exposure-rate
meter. The meter has an internal sodium iodide detector capable of measuring
dose rates between 0 and 5000 μR/h.
d. Thermo FH40GL Dose Rate Meter with FHZ732GM Pancake Probe
The FH40GL is a stand-alone radiation survey meter equipped with an internal
proportional detector capable of measuring γ- and X-radiation exposure rates
from 1 μR/h–10 R/h. The unit is also equipped with an FHX732GM pancake GM
detector capable of measuring count rates from α, β, and γ radiations over a
range of 0.01–100,000 counts per second.
e. Thermo FH40TG TeleprobeTM
The FH40TG telescoping probe can be used with the FH40GL to measure γ- and
X-radiation exposure rates over a range of 10 μR/h–1000 R/h. The probe is
equipped with two GM detectors that can be extended up to 13 feet away from
the user, allowing exposure rate measurements to be made at a distance from
the source.
f. Thermo RO-20 Ionization Chamber
The RO-20 is capable of measuring exposure rates from β, γ, and X radiations.
The instrument is equipped with an air filled ionization detector capable of
measuring exposure rates up to 50 R/h.
g. Thermo PM1703M Gamma Pager
The PM1703M is a pager-sized survey meter that can be worn on the belt. The
meter contains a Csl(Tl) scintillator-photodiode detector capable of measuring
γ- and X-radiation. The instrument will measure exposure rates from 0–5000
μR/h. The PM1703M is a highly sensitive instrument that can be set to alarm
when the background varies by a user-set factor. This meter can be used to
warn the user that they have entered a radiation area that is above background
radiation levels.
B. Scalars
Application and Principle of Operation:
Scalars are used to analyze samples of radioactive material and to quantify
the amount of material present. They are often used to measure the amount of
radioactive material in air samples, wipe samples, and nasal swabs. Scalars
use the same detector types used in survey meters. These instruments can
typically be set to count a sample for a specified time.
Calibration:
Calibration is performed by the manufacturer on a periodic (usually annual)
basis.
HRT Availability:
a. Ludlum Model 3030 Alpha/Beta Scalar
The Ludlum Model 3030 is a dual alpha/beta scalar used for sample counting.
The instrument has a ZnS(Ag) coated scintillation detector capable of
discriminating between α and β radiations. The readout on the front of the
instrument reports both α and β counts for the specified period. Counting time
can be set from 0.1–30 minutes.
b. Ludlum Model 2000 Scalar with 43-10 Alpha Sample Counter
The Ludlum Model 2000 scalar with 43-10 sample counter is capable of counting
samples for α particle emissions. The sample counter has a ZnS(Ag)
scintillation detector. Counting time can be set from 6–990 minutes.
c. Thermo HandECount Scalar
The HandECount is a battery or AC powered sample counter used for determining
the α and β activity present in a sample. The instrument uses a PalmTM
personal digital assistant as the user interface and to record all results.
All data may be transferred to a computer via a conduit program. The
HandECount will report both α and β counts for a sample.
C. Electronic Personal Dosimeters
Application and Principle of Operation:
Electronic personal dosimeters are used to measure the dose received by an
individual. They are normally worn on the front of the body in the chest area.
Most electronic dosimeters measure the deep-dose equivalent (Hp(10)) to γ
radiation. Some electronic dosimeters also measure the shallow dose equivalent
(Hp(0.07)). Most electronic dosimeters allow the user to set alarms for
integrated dose and/or dose rates.
Calibration:
Calibration is performed by the manufacturer on a periodic (usually annual)
basis.
HRT Availability:
Thermo Electronic Personal Dosimeter (EPD) Mk.2
The Thermo EPD Mk.2 is an electronic dosimeter capable of measuring Hp(10)
(deep dose) and Hp(0.07) (shallow/skin dose). It is sensitive to γ and X
radiations for Hp(10) measurements, and is sensitive to γ, β, and X radiations
for Hp(0.07) measurements. Alarms can be set for accumulated doses and for
dose rates for both Hp(10) and Hp(0.07).
Rados RAD-60 Electronic Personal Dosimeters
The Rados RAD-60 is capable of measuring Hp(10) from γ and X radiations.
Alarms can be set for both dose and dose rate.
D. Spectroscopy
Application and Principle of Operation:
Portable handheld radiation spectroscopy instruments allow the user to
identify radionuclides. These instruments typically use a sodium iodide
detector with a multichannel analyzer to measure the energy spectrum emitted
by a radioactive source. The instrument compares the spectrum to a library of
spectra and provides the user with a list of likely sources. Spectra can also
be downloaded to a computer if the user wishes to perform the spectral
analysis manually or wishes to print the spectra for documentation.
Calibration:
Calibration is performed by the manufacturer on a periodic (usually annual)
basis.
HRT Availability:
EXPLORANIUMTM GR-135N
The EXPLORANIUMTM GR-135N is a handheld isotope identification device. The
GR-135N has a sodium iodide detector capable of identifying radionuclides, a
GM detector for measuring exposure rate, and a solid-state neutron detector.
Spectra from the GR-135N can be downloaded to a computer for analysis and
printing.
E. Electret-Passive Environmental Radon Monitoring
Application and Principle of Operation:
The Electret-Passive Environmental Radon Monitor (E-PERM) system is a passive
integrating detector system for the measurement of radon (222Rn) or thoron
(220Rn) concentrations in air. It consists of a charged TeflonTM disk
(electret), an open-faced ionization chamber, and an electret voltage reader.
When the electret is screwed into the chamber, an electrostatic field is
established and a passive ionization chamber is formed. The chamber is
deployed directly in the area to be measured. Radon gas diffuses passively
into the chamber and the α particles emitted from the decay of radon ionize
the air molecules. These ions are then attracted to the charged surface of the
electret, and the charge on the electret is reduced. The electret charge is
measured before and after the exposure with a portable electret voltage
reader, and the rate of change of the charge (change divided by the time of
exposure) is proportional to the concentration of radon in the area.
Calibration:
Calibration factors are provided for each type of electret. Calibration
factors are voltage dependant and instructions for calculating the calibration
factors are in the E-PERM manual provided by the manufacturer.
HRT Availability:
The HRT has 12 E-PERM chambers, electrets, and a voltage reader.
F. Radiation PPE and Shielding
In radioactively contaminated areas, PPE is typically used in order to prevent
employees from becoming contaminated, and to minimize the spread of
radioactive contamination. The choice of appropriate shielding for ionizing
radiation depends on the type and energy of the radiations to be shielded.
Alpha particles have very low penetrating power and travel only a few
centimeters in air and will not penetrate the dead outer layer of skin.
Shielding is generally not required for alpha particles since external
exposure to alpha particles delivers no dose. Beta particles can travel
several meters in air and can penetrate several millimeters into the skin.
Beta particle should be shielded using an appropriate thickness of low atomic
mass (low-Z) materials such as aluminum or plastics. Shielding beta particles
with high-Z materials should be avoided as this can produce bremsstrahlung
radiations. Gamma and x-rays can travel kilometers in air and can penetrate
deep into the human body or pass through it entirely. Gamma and x-rays are
most efficiently shielded using an appropriate thickness of high-Z materials
such as lead or steel, or with an appropriate thickness of concrete. Neutrons
are most efficiently shielded using an appropriate thickness of hydrogenous
materials such as paraffin, water, or plastics, or with an appropriate
thickness of concrete.
NOTE: The HRT also serves as the coordinator for OSHA's Radiation SRT and can
provide additional assistance and technical information regarding radiation
measurements. Special precautions are also necessary to prevent exposure when
working with radioactive materials, such as PPE and/or other work practices.
Contact the HRT for more details.
NONIONIZING RADIATION
A. Survey Meters and Personal Monitors
Application and Principle of Operation:
Radio Frequency (RF) survey meters are used to measure both electric and
magnetic fields from RF sources. RF meters must be selected based on the
frequency of the radiation that is to be measured. Meters typically have
interchangeable probes for measuring electric and magnetic fields. Some meters
and probes are capable of performing spatial and temporal averaging for
multiple frequencies and displaying measurement results in percent of exposure
from guidelines recommended by one of several consensus standards.
RF personal monitors are used to measure personal RF exposures. These monitors
are worn on the belt and continuously log personal exposures and provide an
exposure result using a shaped frequency response.
Induced currents from RF exposure can be measured using a clamp-on induced
current meter. Induced currents in the arms and legs can be measured using
these devices.
Calibration:
No field calibration is available. Calibration is performed by the
manufacturer on a periodic basis.
HRT Availability:
Narda 8860
The Narda 8860 personal RF monitor is used to monitor occupational exposures
to RF sources within the frequency range of 100 kilo Hertz (kHz) – 100 giga
Hertz (GHz). The user can select from multiple alarm settings. The unit
continuously logs RF exposure levels and reports results based on a shaped
frequency response.
- Air Velocity Monitors/Indoor Air Quality (IAQ) Assessment Instrumentation
AIR VELOCITY MONITORS AND METERS
A. Flow Hoods
Application and Principle of Operation:
These instruments measure air velocities at air supply or exhaust outlets. A
flow hood (balometer) is an instrument used to measure volumetric air flow
from supply or exhaust diffusers and grilles. The benefit of using a flow hood
is that accurate measurements with a high degree of precision can be quickly
obtained without the necessity of measuring grille sizes and conducting
repeated velometer measurements over the face of the diffuser. With the flow
hood, the user can measure air volume, check HVAC system balance, verify air
flow distribution within and between rooms, and in combination with other data
estimate the percent of outdoor air being supplied to a space. Additionally,
if the diffuser area is known or measured, an accurate average linear air flow
rate can be calculated. Such applications may be important in assessing
ventilation controls, during IAQ investigations, or any time knowledge of the
existing volumetric airflow is important (e.g., when an air contaminant
violation exists and the employer is relying on dilution ventilation for
contaminant control or when the air flow patterns may be drawing an air
contaminant into an unintended space and causing exposure). For more guidance
on the appropriate use of flow hoods, please contact SLTC.
Calibration:
No field calibration is available. Periodic factory calibration or equivalent
by a laboratory is essential. Equipment should be sent to CTC for coordination
and document retention.
Maintenance:
These instruments typically require little field maintenance other than
battery-pack servicing and zero balancing of the analog scales. (Check
manufacturer's manual.)
B. Thermoanemometer
Application and Principle of Operation:
A thermoanemometer (hotwire anemometer) is a device used to measure air speed
(velocity). Thermoanemometers can be used to monitor the effectiveness of
ventilation systems and direct exhaust systems. They are valuable when
evaluating laboratory hoods for adequate velocity and capture speed. When the
area of the hood face or the diffuser is known (or measured) the volumetric
airflow can be estimated by taking traverse measurements across the face of
the hood or diffuser. Additionally, if a duct has access ports, the interior
duct speed can be estimated. A benefit of using the hotwire anemometer over
the balometer for volumetric flow measurement is the compact size of the
anemometer, but this ease of use becomes more complex once multiple
measurements are required (traversing a hood face) and must be balanced
against the superior precision and accuracy of the balometer. For more
guidance on the appropriate use of thermoanemometers, please contact SLTC.
Calibration:
No field calibration is available. Periodic factory calibration or equivalent
by a laboratory is essential. Equipment should be sent to CTC for calibration
and document retention.
Maintenance:
These instruments typically require little field maintenance other than
battery-pack servicing and zero balancing of analog scales. (Check
manufacturer's manual.)
C. Other Air Velocity Meters
Other air velocity meters include rotating-vane and swinging-vane velometers.
NOTE: Barometric pressure and air temperature should be noted when using air
velocity meters.
D. Bioaerosol Monitors
Application and Principle of Operation:
A bioaerosol meter, usually a two-stage sampler, is also a multi-orifice
cascade impactor. This unit is used when size distribution is not required and
only respirable-nonrespirable segregation or total counts are needed.
Ninety-five to 100 percent of viable particles above 0.8 microns in an aerosol
can be collected on a variety of bacteriological agar. Trypticase soy agar is
normally used to collect bacteria, and malt extract agar is normally used to
collect fungi. Bioaerosol monitors can be used in assessing sick-building
syndrome, or buildings which may have source exposures to molds and bacteria
which may be exacerbating or causing illness to the occupants. These samplers
are also capable of collecting virus particles. However, there is no
convenient or practical method for cultivation and enumeration of these
particles.
Calibration:
Bioaerosol meters must be calibrated before use. This can be done using an
electronic calibration system with a high-flow cell.
Special Considerations:
Prior to sampling, determine the type of collection media required and an
analytical laboratory to provide analysis. The HRT can provide this
information. This specialized equipment is available from the HRT with
instructions.
Maintenance:
The sampler should be decontaminated prior to use by sterilizer, or chemical
decontamination with isopropanol.
- Noise Monitors and Meters
The following sections contain a brief discussion of various types of
instruments that may be used for noise monitoring. Refer to OSHA Technical Manual
Section III, Chapter 5,
"Noise and Hearing Conservation" for additional
information.
A. Sound Level Meters
Application and Principle of Operation:
The sound level meter (SLM) is the basic instrument for investigating noise
levels. It can be used to evaluate area noise levels, to identify noise
sources, estimate employee exposures and aid in determining solutions for
noise control. The SLM consists of a microphone, a preamplifier, an amplifier
with an adjustable and calibrated gain, frequency weighting filters, meter
response circuits, and an analog meter or digital readout. ANSI has classified
levels of precision for sound level meters as Type 0 (laboratory standard),
Type I (precision measurements in the field), and Type II (general purpose
measurements). The Type II meter is most frequently used in the field for
employee exposure and noise evaluation purposes.
Most SLMs allow options for linear, A, and C frequency weighting. In addition,
either "slow" or "fast" meter response can be selected. With fast response,
the meter closely follows the sound level as it changes. A slow response is
more sluggish but allows the user to obtain a better average of the changing
sound level. The OSHA noise standards require exposure measurements to be made
with a slow meter response on the A scale.
Some SLMs have an "impulse" or "peak" response for monitoring impulsive
sounds. The peak value is the maximum value of the waveform, while the impulse
response is an integrated measurement. Only the peak value should be used when
measuring peak levels for compliance with the OSHA 140 decibel (dB) peak sound
pressure level.
B. Noise Dosimeters
Application and Principle of Operation:
A noise dosimeter is essentially an SLM that integrates noise levels over the
sampling period and calculates the noise dose. It is the primary instrument
used for compliance measurements. The noise dosimeter is worn by an individual
during sampling to calculate personal noise dose, or it can be placed in a
specific location to measure the sound level in that area.
Specific instrument settings can be selected on a noise dosimeter, including
exchange rate, frequency weighting, fast or slow response, criterion level,
and threshold. Refer to
Section III, Chapter 5
for additional information.
C. Octave Band Analyzers
Application and Principle of Operation:
An octave band analyzer is a type of SLM which can separate the monitored
noise into specific frequency bands, which is necessary when analyzing noise
sources to develop noise control solutions. This information is also useful in
selecting hearing protectors by calculating the amount of attenuation for
specific frequency bands. Most octave band analyzers filter the sampled noise
spectrum into 9 or 10 octave bands, while some analyzers can measure noise in
one-third octave bands for an even more detailed analysis. Usually, a Type I
(precision) SLM is used for octave band analysis.
D. Sound Intensity Analyzers
Application and Principle of Operation:
Ordinary SLMs measure sound pressure level, which indicates the level of the
sound, but not the direction from which the sound is coming. A sound intensity
analyzer can measure intensity, which is a measure of both the magnitude and
direction of the sound energy. With an intensity analyzer, noise sources can
be specifically identified and ranked according to sound power. This analysis
can often be performed in environments where the noise is reverberant, since
the intensity analyzer indicates the direction of the noise. A sound intensity
analyzer is particularly useful for pinpointing noise sources and determining
appropriate engineering controls.
Calibration:
Noise instruments are usually calibrated at the field site before and after
each use, according to the manufacturer's instructions. Calibration is
accomplished by using an acoustic calibrator which applies a known sound
pressure level to the microphone, and the instrument is adjusted to read the
proper level. In addition to user calibration, some instruments may require
routine factory calibration and maintenance, such as every 1-2 years.
Special Considerations:
Some general considerations for using noise monitoring equipment are listed
below. Each type of equipment should be used according to the manufacturer’s
instructions. Additional factors to consider are included in
Section III,
Chapter 5.
a. Batteries should always be checked prior to use.
b. Be careful with microphone cables. Never kink, stretch, pinch or otherwise
damage the cables.
c. Use a microphone windscreen when equipment is used outdoors or in dusty or
dirty areas.
d. Never use any type of covering on the microphone (e.g., plastic bag or
plastic wrap) to protect it from moisture. These materials will distort the
noise entering the microphone, and the readings will be invalid.
e. Never try to clean a microphone, particularly with compressed air, since
damage is likely to result.
f. Remove the batteries from any meter that will be stored for more than a few
days. Protect meters from extreme heat and humidity.
HRT Availability:
The HRT maintains the following specialized noise analysis equipment which can
be used for noise exposure and engineering control evaluations:
a. Bruel & Kjaer 2260 Analyzer
The B&K 2260 is a multipurpose Type I sound level meter and octave band
analyzer. It can also be operated as a sound intensity analyzer for
identifying noise sources and determining engineering controls. In addition,
the 2260 includes a building acoustics system for measuring noise decay and
determining the reverberation characteristics for a given room. Based on the
noise decay data, calculations can be performed to estimate potential noise
reduction if absorptive materials are applied to room surfaces, such as the
walls and ceiling.
b. Larson Davis Spark™ 705 Dosimeters
The Larson Davis Spark 705 Dosimeter is a super-duty dosimeter contained in a
sealed, waterproof, intrinsically safe metal housing. The dosimeters have no
controls or displays, which eliminates the possibility of tampering or damage
by the individual wearing the monitor. The dosimeters are programmed and
controlled by use of a remote control unit or personal computer. The remote
control unit (model 706RC) can also be operated as an additional dosimeter.
Data is transferred from the 705 via an infrared port on the dosimeter
housing.
- Vibration Monitors
The following sections contain a brief discussion of various types of
measurements that are of concern when measuring vibration. Human response to
vibration is dependant on several factors, including the frequency, amplitude,
direction, point of application, time of exposure, clothing and equipment,
body size, body posture, body tension, and composition. A complete assessment
of exposure to vibration requires the measurement of acceleration in
well-defined directions, frequencies and duration of exposure. The vibration
will generally be measured along 3 (x, y and z) axes.
A typical vibration measurement system includes a device (accelerometer) to
sense the vibration, a recorder, a frequency analyzer, a frequency-weighting
network, and a display such as a meter, printer or recorder. The accelerometer
produces an electrical signal in response to the vibration. The size of this
signal is proportional to the acceleration applied to it. The frequency
analyzer determines the distribution of acceleration in different frequency
bands. The frequency-weighting network mimics the human sensitivity to
vibration at different frequencies. The use of weighting networks gives a
single number as a measure of vibration exposure (i.e., units of vibration)
and is expressed in meters per second squared (m/s2).
A. Hand-arm Vibration
Application and Principle of Operation:
Hand-arm vibration will generally be measured when using a hand-held power
tool. First, one must determine the type of vibration that will be encountered
since a different accelerometer will be used depending on whether an impact
(e.g., jack hammer or chipper) or non-impact (e.g., chain saws or grinders)
tool is being used. The accelerometer will be attached to the tool so the axes
are measured while the employee grasps the tool handle. The z axis is
generally from the wrist to the middle knuckle, the x axis is from the top of
the hand down through the bottom of the hand and wrapped fingers, and the y
axis runs from right to left across the knuckles of the hand. The measurement
should be made as close as possible to the point where the vibration enters
the hand.
The frequency-weighting network for hand-arm vibration is given in the
International Organization for Standardization (ISO) standard ISO 5349. The
human hand does not appear to be equally sensitive to vibration energy at all
frequencies. The sensitivity appears to be the highest around 8-16 Hz (Hertz
or cycles per second), so the weighting networks will generally emphasize this
range. Vibration amplitudes, whether measured as frequency-weighted or
frequency-independent acceleration levels (m/sec2), are generally used to
describe vibration stress (American National Standards Institute, American
Conference of Governmental Industrial Hygienist, ISO, BSI). These numbers can
generally be read directly from the human vibration meter used.
The recommendations of most advisory bodies are based on an exposure level
likely to cause the first signs of Stage II Hand-Arm Vibration Syndrome (white
finger) in employees.
B. Whole-body Vibration
Application and Principle of Operation:
The measurement of whole-body vibration is important when measuring vibration
from large pieces of machinery which are operated in a seated, standing, or
reclined posture. Vibration is measured across three (x, y and z) axes. The
orientation of each axis is as follows: z is from head to toe, x is from front
to back and y is from shoulder to shoulder. The accelerometer must be placed
at the point where the body comes in contact with the vibrating surface,
generally on the seat or against the back of the operator.
The measurement device is generally an accelerometer mounted in a hard rubber
disc. This disc is placed in the seat between the operator and the machinery.
Care should be taken to ensure that the weight of the disc does not exceed
more than about 10% of the weight of the person being measured.
Calibration:
Vibration equipment will not generally be calibrated by the user. These
devices will generally be sent back to the manufacturer for calibration on an
annual basis.
Special Considerations:
OSHA does not have standards concerning vibration exposure. The American
Conference of Governmental Industrial Hygienists (ACGIH) has developed
Threshold Limit Values (TLVs) for vibration exposure to hand-held tools. The
exposure limits are given as frequency-weighted acceleration. The frequency
weighting is based on a scheme recommended in ISO 5349. Vibration-measuring
instruments have a frequency-weighting network as an option. The networks list
acceleration levels and exposure durations to which, ACGIH has determined,
most employees can be exposed repeatedly without severe damage to fingers.
ACGIH advises that these values be applied in conjunction with other
protective measures, including vibration control.
The most widely used document on whole-body vibration is the "Guide for the
Evaluation of Human Exposure to Whole Body Vibration (ISO 2631)." These
exposure guidelines have been adopted as ACGIH TLVs.
The ISO standard suggests three different types of exposure limits for whole
body vibration, of which only the third is generally used occupationally and
is the basis for the ACGIH standard:
1. The reduced-comfort boundary is for the comfort of passengers in airplanes,
boats, and trains. Exceeding these exposure limits makes it difficult for
passengers to eat, read or write when traveling.
2. The fatigue-decreased proficiency boundary is a limit for time-dependent
effects that impair performance. For example, fatigue impairs performance in
flying, driving and operating heavy vehicles.
3. The exposure limit is used to assess the maximum possible exposure allowed
for whole-body vibration. There are two separate tables for exposures. One
table is for longitudinal (head to toe; z axis) exposures, with the lowest
exposure limit at 4 - 8 Hz based on human body sensitivity. The second table
is for transverse (back to chest and side to side; x and y axes) exposures,
with the lowest exposure limit at 1– 2 Hz based on human body sensitivity. A
separate set of "severe discomfort boundaries" is given for 8-hour, 2-hour and
30-minute exposures to whole-body vibration in the 0.1–0.63 Hz range.
ACGIH recommendations are based on exposure levels that should be safe for
repeated exposure, with minimal risk of adverse effects (including pain) to
the back and the ability to operate a land-based vehicle.
Some general considerations for using vibration equipment include:
a. Batteries should always be checked prior to use.
b. Be careful with electrode cables. Never kink, stretch, pinch or otherwise
damage the cables.
c. Remove the batteries from any meter that will be stored for more than a few
days.
d. Protect meters from extreme heat and humidity.
HRT Availability:
The HRT maintains the following vibration analysis equipment:
a. Larson Davis Human Vibration Meter - HVM100
The HVM is a portable multipurpose meter which can be used for measurement of
whole-body vibration, hand-arm vibration, hand-tool vibration, vibration
severity and product compliance testing. It will collect and analyze data in
accordance with the most current ISO requirements for hand-arm vibration and
whole-body vibration exposures. It measures three input channels
simultaneously, and a fourth channel calculates and stores vector sum
information. Single and triaxial accelerometers attach to specialized
mechanical mounting adaptors to allow measurement on a wide variety of tools
and surfaces.
C. Mechanical Force Gauge for Ergonomic Evaluations
Application and Principle of Operation:
Mechanical force gauges are frequently used for a wide range of force testing
applications including testing of compressive and/or tensile forces. The
gauges may be mounted to a test stand for even greater control and consistent
results in repetitive testing applications. An easy to read concentric dial
measures clockwise direction only. The dial rotates 360-degrees for tarring. A
peak hold button captures peak readings. Usually the gauges are available in
lbf, kgf or N units of measure.
Calibration:
Gauge accuracy should be checked periodically to ensure the gauge is within
its calibration limits. The calibration can be verified by applying known
weight (adjusted for local gravity) to the extension hook. If adjustment is
required, the gauge should be returned to the manufacturer for calibration.
- Electronic Test Equipment
A. Electronic Testing Meters
Application and Principle of Operation:
Electrical testing meters include multimeters, clip-on current meters,
megohmmeters, battery testers, ground-wire impedance testers, 120-V AC
receptacle testers, ground–fault interrupt testers, electrostatic meters, and
AC voltage detectors. Multimeters measure AC or DC voltage or current and
resistance. They can check for AC leakage, proper line voltage, batteries,
continuity, ground connection, integrity of shielded connections, fuses, etc.
Other specialized equipment is described in Appendix II: 3-3.
Calibration:
Few, if any, field calibrations are available. Check manufacturer's manual.
Periodic calibration is handled by the CTC.
Maintenance:
No field maintenance is required other than battery-pack servicing.
- Heat Stress Instrumentation
The following sections contain a brief discussion of various types of
instruments that may be used for heat and heat stress monitoring. Refer to
OSHA Technical Manual
Section III, Chapter 4, "Heat Stress" for additional
information on heat-related injuries and illnesses.
Application and Principle of Operation:
There are two types of heat stress monitors available through the CTC. One
type is a real-time area monitor that measures environmental conditions that
contribute to heat stress and the other is a real-time personal monitor that
measures the wearer’s body temperature and/or heart rate. The area monitor
(Quest model QuestempTM 15 or IST WiBGeTTM model RSS-214) measures indoor and
outdoor wet bulb globe temperatures (WBGT). The temperature values can be data
logged and the monitor can also be configured to sound an alarm when a
predetermined WBGT is reached. The personal monitors provide real-time
information on the wearer's physiological condition and work by either
inserting a probe into the wearer's ear canal to monitor body temperature
(Quest Technologies Questemp IITM) or wearing a sensor belt around the waist
that monitors heart rate and temperature (Metrosonics hs383 Personal Heat
Stress Monitor). Both personal devices can be programmed to alarm when a
predetermined temperature or heart rate is exceeded.
The area monitors work by taking measurements of the ambient temperature, the
wet bulb temperature and the globe temperature and then using a formula to
determine the WBGT. The wet bulb temperature takes into account the effects of
humidity on the body's cooling mechanism and the globe temperature accounts
for radiant heat on the employee. Outdoors, a WBGT is calculated by
multiplying the wet bulb temperature by 0.7, the globe temperature by 0.2 and
the dry bulb temperature by 0.1. Since radiant heat from the sun is not a
factor indoors (or outdoors without a radiant heat load), the WBGT is
calculated differently for indoor environments; the wet bulb multiplier stays
the same, the globe temperature is multiplied by 0.3 and the dry bulb
temperature drops out of the formula.
Another personal heat stress monitoring system is available through the HRT.
The CorTempTM personal heat stress monitoring system uses an ingestible
temperature sensor that is swallowed by the person being monitored. The
capsule transmits the employee's core temperature to a receiver on his/her
belt which also receives a heart rate monitor's reading and then transmits
both signals to a receiver monitored by an observer up to 100 yards away.
Since the sensor must be swallowed, the CorTempTM system is considered a
medical device and must be used under the supervision of a physician.
Calibration:
Most calibration is done annually by the manufacturer. Certain instruments
have simple user calibrations that must be performed before each use. The
QuestempTM 15 is provided with a calibration module that plugs into the
monitor. If the temperatures reported by the module and the monitor differ by
more than 0.5 °C, the monitor needs to be returned to the manufacturer for
calibration. The QuestempTM II personal heat stress monitor is calibrated to
the user's body temperature every time it is used or if the ambient
temperature changes by 10°C.
NOTE: Any discussion regarding a specific manufacturer’s product is not meant
to imply approval or promotion by OSHA, but merely reflects the need to convey
specific information which is pertinent to the particular type and brand of
instrumentation available for OSHA personnel.
APPENDIX II: 3–1.
A. Batteries
1. Alkaline batteries must be replaced frequently before they become depleted.
For any full shift sampling, instrument batteries should be checked with a
voltage meter to ensure a full charge, or fresh batteries should be used. When
replacing batteries, never mix types (alkaline, carbon zinc, etc.), capacity,
or age. Doing so can have negative affects on all the batteries. Remove
batteries if equipment will not be used for an extended period of time.
2. Rechargeable Batteries
a. Nickel cadmium batteries (Ni-Cad) are the most common rechargeable battery
in industrial hygiene use today. They have numerous advantages over alkaline
batteries if they are treated properly. If not treated properly, Ni-Cad
batteries can develop a "memory." "Memory" occurs when a battery develops a
usage pattern that can prevent the battery from holding a charge for a long
usage period.
i. A fully charged Ni-Cad battery will hold 1.35 volts per cell. Batteries are
usually rated at 1.2 volts per cell, so you can determine the number of cells
a battery contains by dividing the total rated voltage by 1.2.
ii. Do not discharge a multi-cell Ni-Cad battery pack to a voltage level below
1.0 volts per cell; doing this will drive a reverse current through some of
the cells and can permanently damage them.
iii. Rechargeable Ni-Cad batteries should be charged only in accordance with
manufacturer's instructions. Chargers are generally designed to charge
batteries in approximately 8–16 hours at a high charge rate. A battery can be
overcharged and ruined when a high charge rate is applied for too long a time.
However, Ni-Cad batteries may be left on a proper trickle charge indefinitely
to maintain them at peak capacity. In this case, discharging for a period
equal to the longest effective field service time may be necessary because of
short-term memory imprinting. However, do not let the battery discharge
overnight or longer. Turn the instrument OFF when the battery reaches the
proper discharge level.
iv. To avoid memory development, batteries should be exercised before field
use, and occasionally after being put into field use. Before field use, the
battery pack should be charged and discharged to a "low battery" state three
times.
NOTE: Battery care is important in assuring uninterrupted sampling. A pump
battery pack, for example, should be discharged to the recommended level
before charging, at least after every use, and three times before the first
use. If the pump is allowed to run down until the battery reaches the low
battery Fault condition, the pump should be turned OFF soon after the Fault
condition stops the pump. Leaving some pumps (such as the GilAir) ON for a
long time after this Fault condition can damage the battery pack. Also, avoid
overcharging the battery pack.
b. Nickel-Metal Hydride Batteries (NMH) are similar to Ni-Cad batteries but
are less prone to develop a memory and typically offer up to 40% more
run time. They should be charged similarly to Ni-Cad batteries, but do not
need the periodic discharge to 1.0 volts.
c. Lithium Ion and Lithium Polymer Batteries are the latest in battery
technology, offering an energy density approximately twice that of Ni-Cad
batteries, and they also have a very low self-discharge rate.
APPENDIX II: 3–2.
A. Availability, Calibration, Maintenance and Repair of Equipment: Cincinnati
Technical Center (CTC)
For information regarding the availability of specific equipment, OSHA staff
should access the Cincinnati Technical Center (CTC) website. The CTC
calibrates and repairs equipment and instruments, and it serves as a source of
technical information on instruments and measurement technology. Equipment
servicing information, including service intervals and technical equipment
status, can also be found on the CTC website. The OSHA SLTC Program Support
Division, including the HRT, also has some specialized equipment available for
Agency use.
APPENDIX II: 3–3.
A. Instrument Chart
The information shown in the table below is for reference only. Not every
compliance officer or field office will have every type of instrument. Many of
the instruments can be found in, and are available through, the CTC's loan
program or through the SLTC.
INSTRUMENT USE
|
Type of instrument |
Measured substance |
Application |
|
|
|
Physical Measurements
|
Electrobalances
|
Any weighable
|
Filter weighing
|
Stop time meter
|
Time
|
Calibration
|
Tachometers
|
Mechanical speed
|
Flywheels, belts, cylinders, lathes, etc.
|
Electrical testers
|
Electricity
|
Circuits
|
Mulitimeters
|
Electricity
|
Circuits
|
Noise dosimeters
|
Noise
|
Noisy locations
|
SLM kits, type 1
|
Noise
|
Noisy locations |
Omnicals
|
Noise meter calibration
|
Noise meters
|
Vibration meters
|
Excessive vibration
|
Bearings, gear trains, housings, walls
|
Thermoanemometer
|
Air movement
|
Ventilation
|
Hand pumps
|
Detector tubes
|
Screening
|
Pressure guages
|
Air Pressure
|
Compressor air lines
|
Pumps, low flow
|
Air volume
|
Sampling with adsorbent tubes
|
Pumps, medium flow
|
Air volume
|
Sampling
|
Gilibrators
|
Air pump calibration
|
Pump calibration
|
Fibrous aerosol monitors
|
Fibers in air
|
Asbestos
|
Dust monitors
|
Respirable dust
|
Mines, sandblasting, dusty operations
|
|
Respirable dust, particles
|
Indoor air, QNFT
|
Soil test kit
|
Soil quality
|
Trenching, excavating
|
|
GAS & VAPOR METERS
|
Type of instrument |
Measured substance |
Application |
|
|
|
Double-range meters
|
Combustible gas, O2
|
Confined spaces
|
Triple range meters
|
1 Gas, O2, combustible gas
|
Confined spaces
|
Quad range meters
|
2 gases, O2, combustible gas
|
Confined spaces
|
CO dosimeter
|
CO
|
Garages, indoor air quality
|
Carbon dioxide meter
|
CO2
|
Indoor air quality
|
Infrared analyzers
|
CO, CO2, organic substances
|
Indoor air, leaks, spills
|
Hydrogen cyanide monitors
|
Hydrogen cyanide
|
Industrial facilities
|
Hydrogen sulfide meters
|
Hydrogen sulfide
|
Farms, sewers
|
Mercury vapor meters
|
Mercury
|
Mercury plants, spills
|
NO and NO2 meters
|
NO and NO2
|
Combustion
|
Ozone analyzers
|
O3
|
Water or air purification, IAQ
|
|
RADIATION METERS
|
Type of instrument |
Measured substance |
Application |
|
|
|
Heat stress meters
|
Ambient (environmental) heat
|
Foundries, furnaces, and ovens
|
Photoionization
|
Ionizable substances
|
Indoor air, leaks, spills
|
Light meters
|
Light
|
Indoor lighting, UV exposure
|
Nonionizing radiation meters
|
Nonionizing radiation
|
Communications, microwaves, heaters
|
Ionizing radiation meters
|
Ionizing radiation
|
Nuclear waste or plants
|
Electrostatic field tester
|
Static electric fields
|
Hazardous locations
|
RF instruments
|
Electromagnetic fields
|
RF heat sealers, VDTs, induction motors
|
|
BIOLOGICAL MONITORS
|
Type of instrument |
Measured substance |
Application |
|
|
|
Microbial sampler |
Microbes |
Indoor air quality |
|
|