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OSHA TECHNICAL MANUAL TABLE OF CONTENTS NEXT CHAPTER


SECTION II: CHAPTER 3
TECHNICAL EQUIPMENT
Contents:
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII. 		Introduction
Calibration
Batteries
Adverse Conditions
Direct-Reading Instruments
Bioaerosol Monitors
Radiation Monitors and Meters
Air Velocity Monitors and Meters
Noise Monitors and Meters
Electronic Testing Meters
Heat Stress Instruments
Bibliography


Appendix II:3-1.   Calibration Intervals
Appendix II:3-2.   General Procedures for Returning Instruments
Appendix II:3-3.   Instrument Chart

  1. INTRODUCTION.

    The Directorate of Technical Support provides the overall management of technical equipment, including calibration and maintenance. Each person to whom technical equipment is assigned is responsible for ensuring that the equipment is properly maintained and calibrated according to Agency schedules.

    This chapter discusses the types, calibration, maintenance, and operation of equipment commonly used by OSHA compliance personnel in the field. It is not a comprehensive discussion of all available equipment, nor a review of technical equipment. Mention of a specific product is not meant to imply approval or promotion by OSHA, but merely indicates past procurement policy. Some technical equipment can be connected to a computer for calculations and printouts. Consult the manufacturer's manual or call the OSHA Cincinnati Technical Center (CTC).

  2. CALIBRATION.

    OSHA's Cincinnati Technical Center (CTC) calibrates and repairs equipment and instruments, and it serves as a source of technical information on instruments and measurement technology.

    1. SHIPPING INSTRUCTIONS. Equipment shall be packed and sent to the CTC when repairs are necessary, calibration is due, or when a valid reason exists for requesting a more frequent calibration or check of the equipment. Send all parts of the instrument, not just those needing repairs. If the instrument needs repairs or any special attention, attach a note to the instrument stating the associated problem as clearly as possible. Call the CTC, if there are any questions.

      1. Cahn balances shall be repaired by the manufacturer or by local skilled repair companies.

      2. Equipment needing regular calibration by the CTC is listed in Appendix II:3-1.

      3. Send the Maintenance and Calibration Instrument Service Request (OSHA-79 Form, Rev. May 1981) in each box of equipment, and list the equipment in that box.

      4. Use one line per item.

      5. Enter the instrument's description, the manufacturer's code, model code, and serial number.

      6. Enter the return address.

      7. List repairs needed and special instructions on a tag or note attached to the instrument. Include the name and telephone number of a contact person.

      8. Place the equipment in a clean plastic bag. Packing material should be polystyrene foam, polyurethane foam, or crumpled newspaper. Do not use vermiculite, woodchips, or other fibrous or powdery material that may create fine dust, and clog the instrument(s).

      9. Do not send in equipment which has been contaminated. All contaminated equipment should be decontaminated on-site after use. If equipment must be sent in to the CTC after it has been decontaminated, indicate such, including what the equipment was contaminated with. This information should be clearly shown on the OSHA-79, as well as the the individual piece of equipment being tagged and identified.

    2. POSTAL REGULATIONS. Packages to be shipped by the postal service cannot exceed 100 inches in length plus girth or 40 pounds in weight. All markings (old registration, certification, addresses, etc.) must be removed from reused shipping containers or covered so that only new markings are visible.

    3. OTHER SHIPPING MODES. There are other shipping alternatives (UPS, Fed Ex, etc.) to the Postal Service. The regulations of any private shipping concern will need to be followed as well as Department of transportation regulations.

    4. SPECIAL INSTRUCTIONS.

      1. Instruments requiring repair or special instructions must be tagged with the symptoms of the malfunction and/or the special instruction written on the tag, including the contact person. The special instructions in Appendix II:3-2 may apply. All hazardous materials must be marked and the carrier informed.

      2. The CTC has specialized equipment in addition to that described here. This equipment is available on loan. Contact the CTC directly for all loans.

      3. The Health Response Team (HRT) and the Salt Lake Technical Center (SLTC) may sometimes have specialized equipment such as ozone meters, portable gas chromatographs, and radon and bioaerosol monitors available for field use. Contact HRT and SLTC for further information.

  3. BATTERIES.

    1. ALKALINE BATTERIES. Replace frequently before they become depleted, or carry fresh replacements. When replacing a battery, never mix types (alkaline, carbon zinc, etc.) or capacity and 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 NI-CAD BATTERIES.

      1. Check the batteries under load (e.g., turn pump on and check voltage at charging jack, if one is available and this can be done safely) before use. See manufacturer's instructions for locations to check voltage. Use 1.2 volts per Ni-Cad cell for an estimate of the fully charged voltage of a rechargeable battery pack.

      2. It is undesirable to discharge a multicell Ni-Cad battery pack to voltage levels that are below 1.0 volts per cell; doing this will drive a reverse current through some of the cells and can permanently damage them.

      3. Rechargeable Ni-Cad batteries should be charged only in accordance with manufacturer's instructions. Chargers are generally designed to charge batteries in approximately 8 to 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 run down overnight or longer. Turn the instrument OFF when the battery reaches the proper discharge level.

        NOTE:   Battery care is important in assuring uninterruted sampling. A pump battery pack, for example, should be discharged to the recommended level before charging, at least every their 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.

    3. OTHER RECHARGEABLE BATTERIES. Other types of rechargeable batteries are being used in equipment such as lead-acid, nickel-metal hydride, etc. Make sure the manufacturer's instructions are followed concerning the handling and recharging of these types of batteries.

  4. ADVERSE CONDITIONS.

    1. ADVERSE TEMPERATURE EFFECTS. High ambient temperature, above 100°F and/or radiant heat (e.g., from nearby molten metal) can cause flow faults in air sampling pumps. If these conditions are likely, use the pump with a higher operating temperature range, as opposed to a pump with a lower operating temperature range. Temperature can also affect the accuracy of instrument readings or operation. Check the operating manual for the proper operating temperature range.

    2. EXPLOSIVE ATMOSPHERES.

      1. 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 (NRTL; see 29 CFR 1910.7) for use in the type of atmosphere present. Check the class and division ratings.

      2. When batteries are being replaced, use only the type of battery specified on the safety approval label.

      3. Do not assume that an instrument is intrinsically safe. Verify by contacting the instrument's maker or the CTC, if uncertain.


    3. ATMOSPHERES CONTAINING CARCINOGENS. A plastic bag should be used to cover equipment when carcinogens are present. Decontamination procedures for special environments are available through the Directorate of Technical Support and should be followed after using equipment in carcinogenic environments. If at all possible, decontaminate the equipment after use on-site.

  5. DIRECT-READING INSTRUMENTS.

    1. MERCURY ANALYZER-GOLD FILM ANALYZER.

      1. Description and Application. This instrument is available from the CTC's loan program (ALEP). A gold-film analyzer draws a precise volume of air over a gold-film sensor. A microprocessor computes the concentration of mercury in milligrams per cubic meter and displays the results on the digital meter. The meter is selective for mercury and eliminates interference from water vapor, sulfur dioxide, aromatic hydrocarbons, and particulates. However, hydrogen sulfide is an interferant.

      2. Calibration. Calibration should be performed by the manufacturer or a laboratory with the special facilities to generate known concentrations of mercury vapor. Instruments should be returned to the manufacturer or a calibration laboratory on a scheduled basis.

      3. Special Considerations. In high concentrations of mercury vapor the gold film saturates quickly. Check operating manual for more specific information.

      4. Maintenance. Mercury vapor instruments generally contain rechargeable battery packs, filter medium, pumps, and valves which require periodic maintenance. Except for routine charging of the battery pack, most periodic maintenance will be performed during the scheduled annual calibrations. However, depending on usage, routine maintenance should also include burning mercury deposits off of the gold-film and changing the zero filter when necessary. See operating manual for specific instructions.


    2. OZONE METER.

      1. Description and Application. This instrument is available from the SLTC. The detector uses a thin-film semiconductor sensor. A thin-film platinum heater is formed on one side of an alumina substrate. A thin-film platinum electrode is formed on the other side, and a thin-film semiconductor is formed over the platinum electrode by vapor deposition. The semiconductor film, when kept at a high temperature by the heater, will vary in resistance due to the absorption and decomposition of ozone. The change in resistance is converted to a change of voltage by the constant-current circuit.

        The measuring range of the instrument is 0.01 ppm to 9.5 ppm ozone in air. The readings are displayed on a liquid crystal display that reads ozone concentrations directly. The temperature range is 0°-40° C, and the relative humidity range is 10%-80% RH.

      2. Calibration. Calibrate instrument before and after each use. Be sure to use a well-ventilated area since ozone levels may exceed the PEL for short periods. Calibration requires a source of ozone. Controlled ozone concentrations are difficult to generate in the field, and this calibration is normally performed at SLTC. Gas that is either specially desiccated or humidified must not be used for preparing calibration standards, as readings will be inaccurate.

      3. Special Considerations.

        a.  The instrument is not intrinsically safe.

        b.  The instrument must not be exposed to water, rain, high humidity, high temperature, or extreme temperature fluctuation.

        c.  The instrument must not be used or stored in an atmosphere containing silicon compounds, or the sensor will be poisoned.

        d.  The instrument is not to be used for detecting gases other than ozone. Measurements must not be performed when the presence of organic solvents, reducing gases (such as nitrogen monoxide, etc.), or smoke is suspected; readings may be low.

      4. Maintenance. The intake-filter unit-Teflon sampling tube should be clean and connected firmly. These should be checked before each operation. Check pump aspiration and sensitivity before each operation.


    3. TOXIC GAS METERS.

      1. Description and Application. This analyzer uses an electrochemical voltametric 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. Since the method of analysis is not absolute, prior calibration against a known standard is required. Exhaustive tests have shown the method to be linear; thus, calibration at a single concentration, along with checking the zero point, is sufficient.

        Types:   sulfur dioxide, hydrogen cyanide, hydrogen chloride, hydrazine, carbon monoxide, hydrogen sulfide, nitrogen oxides, chlorine, and ethylene oxide. Can be combined with combustible gas and oxygen meters.

      2. Calibration. Calibrate the direct-reading gas monitor before and after each use in accordance with the manufacturer's instructions and with the appropriate calibration gases.

      3. Special Considerations.

        a.  Interference from other gases can be a problem. See manufacturer literature.

        b.  When calibrating under external pressure, the pump must be disconnected from the sensor to avoid sensor damage. If the span gas is directly fed into the instrument from a regulated pressurized cylinder, the flow rate should be set to match the normal sampling rate.

        c.  Due to the high reaction rate of the gas in the sensor, substantially lower flow rates result in lower readings. This high reaction rate makes rapid fall time possible simply by shutting off the pump. Calibration from a sample bag connected to the instrument is the preferred method.


    4. PHOTOIONIZATION METERS.

      1. Description and Applications. Ionization is based upon making a gas conductive by the creation of electrically charged atoms, molecules, or electrons and the collection of these charged particles under the influence of an applied electric field. The photoionization analyzer is a screening instrument used to measure a wide variety of organic and some inorganic compounds. It is also useful as a leak detector.

        The limit of detection for most contaminants is approximately 0.1 ppm.

      2. Calibration. The procedure for calibration involves applying the calibration gas (typically 100 ppm isobutylene) to the instrument and checking the reading.

      3. Special Considerations. The specificity of the instrument depends on the sensitivity of the detector to the substance being measured, the number of interfering compounds present, and the concentration of the substance being measured relative to any interferences. Many models now have built-in correction or correlation factors. After calibrating the unit on isobutylene, select the gas to be measured. The instrument will automatically correct for the relative sensitivity of the gas selected. Some instruments are listed by an NRTL for hazardous locations. Check the operating manual for specific conditions.

      4. Maintenance. Keeping these instruments in top operating shape means charging the battery, cleaning the ultraviolet lamp window and light source, and replacing the dust filter. 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, however, and do not attempt to clean while the instrument is connected to line power.


    5. INFRARED ANALYZERS.

      1. Description and Applications. The infrared analyzer has been used within OSHA as a screening tool for a number of gases and vapors (contact the SLTC or the CTC) and is presently the recommended screening method for substances with no feasible sampling and analytical method. See Chemical Sampling Information in OCIS for specific substances. These analyzers are often factory-programed to measure many gases and are also user-programmable to measure other gases.

        A microprocessor automatically controls the spectrometer, averages the measurement signal, and calculates absorbance values. Analysis results can be displayed either in parts per million (ppm) or absorbance units (AU). The variable path-length gas cell gives the analyzer the capability of measuring concentration levels from below 1 ppm up to percent levels.

        Some typical screening applications are:

        • Carbon monoxide and carbon dioxide, especially useful for indoor air assessments;

        • Anesthetic gases including, e.g., nitrous oxide, halothane, enflurane, penthrane, and isoflurane;

        • Ethylene oxide; and

        • Fumigants including e.g. ethylene dibromide, chloropicrin, and methyl bromide.

      2. Calibration. The analyzer and any strip-chart recorder should be calibrated before and after each use in accordance with the manufacturer's instructions.

      3. Special Considerations. The infrared analyzer may be only semispecific for sampling some gases and vapors because of interference by other chemicals with similar absorption wavelengths.

      4. Maintenance. No field maintenance of this device should be attempted except items specifically detailed in the instruction book such as filter replacements and battery charging.


    6. DIRECT-READING PARTICLE MONITORS.

      1. Condensation Nuclei.

        a.  Description and Applications. Condensation-nuclei counters are based upon a miniature, continuous-flow condensation nucleus counter (CNC) that takes particles too small to be easily detected, enlarges them to a detectable size, and counts them. Submicrometer particles are grown to supermicrometer alcohol droplets by first saturating the particles with alcohol vapor as they pass through a heated saturator lined with alcohol soaked felt, and then condensing 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 dust monitors.

        The counter counts 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 insensitive to variations in size, shape, composition, and refractive index.

        b.  Calibration. Check the counter before and after each use in accordance with the manufacturer's instructions. This usually involves checking the zero of the instrument. Annual calibration is handled through the CTC.

        c.  Special Considerations. Reagent-grade isopropyl alcohol for use in these types of instruments is available from the CTC's expendable supply program (AESP).

        • 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.

        • Install the tube plugs into the ends of the twin-tube assembly.


        d.  Maintenance. Isopropyl alcohol must be added to the unit every 5-6 hours of operation, per the manufacturer's instructions. Take care not to overfill the unit. Under normal conditions, a fully charged battery pack will last for about 5 hours of operation. Low battery packs should be charged for at least 6 hours, and battery packs should not be stored in a discharged condition.

      2. Photodetection.

        a.  Description and Applications. Photodetectors operate on the principle of the detection of scattered electromagnetic radiation in the near infrared. 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.

        b.  Calibration. Factory calibration is adequate.

        c.  Special Considerations. Certain instruments have been designed to satisfy the requirements for intrinsically safe operation in methane-air mixtures.

        d.  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 in or exposure to particulate-laden air, the interior walls and the two glass windows of the sensing chamber may have 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 to the radiation passing through the glass windows of the sensing chamber.


    7. COMBUSTIBLE GAS METERS.

      1. Description and Applications. 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.

        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 toxic gases. Some units have an audible alarm that warns of low oxygen levels or malfunction.

      2. Calibration. Before using the monitor each day, calibrate the instrument to a known concentration of combustible gas (usually methane) equivalent to 25%-50% LEL full-scale concentration.

        The monitor must be calibrated to the altitude at which it will be used. Changes in total atmospheric pressure from changes in altitude will influence the instrument's measurement of the air's oxygen content. The unit's instruction manual provides additional details on calibration of sensors.

      3. Special Considerations.

        a.  Silicone compound vapors, leaded gasoline, and sulfur compounds will cause desensitization of the combustible sensor and produce erroneous (low) readings.

        b.  High relative humidity (90%-100%) causes hydroxylation, which reduces sensitivity and causes erratic behavior including inability to calibrate.

        c.  Oxygen deficiency or enrichment such as in steam or inert atmospheres will cause erroneous readings for combustible gases.

        d.  In drying ovens or unusually hot locations, solvent vapors with high boiling points may condense in the sampling lines and produce erroneous (low) readings.

        e.  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.

        f.  High-molecular-weight alcohols can burn out the meters filaments.

        g.  If the flash point is greater than the ambient temperature, an erroneous (low) concentration will be indicated. If the closed vessel is then heated by welding or cutting, the vapors will increase and the atmosphere may become explosive.

        h.  For gases and vapors other than those for which a device was calibrated, users should consult the manufacturer's instructions and correction curves.

      4. 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. Check the bridge sensors periodically, at least every six months, for proper functioning. A thermal combustion-oxygen sensor uses electrochemical cells to measure combustible gases and oxygen. It is not widely used in the area offices.


    8. OXYGEN METERS. These oxygen-measuring devices can include coulometric and fluorescence measurement, paramagnetic analysis, and polarographic methods. The output of most electrochemical oxygen sensors is dependent on the partial pressure of oxygen in the atmosphere. They do not actually measure concentration directly. An instrument calibrated at sea level and used at higher elevations, such as mountains, will indicate a value lower than the actual concentration.

  6. BIOAEROSOL MONITORS.

    1. DESCRIPTION AND APPLICATIONS. A bioaerosol meter, usually a two-stage sampler, is also a multiorifice 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 use to collect fungi. They can be used in assessing sick- (or tight-) building syndrome and mass psychogenic illness.

      These samplers are also capable of collecting virus particles. However, there is no convenient, practical method for cultivation and enumeration of these particles.

    2. CALIBRATION. Bioaerosol meters must be calibrated before use. This can be done using an electronic calibration system with a high-flow cell, available through the HRT.

    3. SPECIAL CONSIDERATIONS. Prior to sampling, determine the type of collection media required and an analytical laboratory. The HRT can provide this information. This specialized equipment is available from the HRT with accompanying instructions.

    4. MAINTENANCE. The sampler should be decontaminated prior to use by sterilizer or chemical decontamination with isopropanol.


  7. RADIATION MONITORS AND METERS.

    1. LIGHT.

      1. Description and Applications. The light meter is a portable unit designed to measure visible, UV, and near-UV light in the workplace. (The CTC has a UV light meter available through its loan program, ALEP.)

        The light meter is capable of reading any optical unit of energy or power level if the appropriate detector has been calibrated with the meter. The spectral range of the instrument is limited only by the choice of detector.

        Steady-state measurements can be made from a steady-state source using the "normal operation" mode. Average measurements can be obtained from a flickering or modulated light source with the meter set in the "fast function" position. Flash measurements can be measured using the "integrate" function. (OSHA currently does not own any light meters with integrating capacity.)

      2. Calibration. No field calibration is available. These instruments are generally very stable and require only periodic calibration. Units should be sent to the CTC for calibration.

      3. Special Considerations. Exposure of the photomultiplier to bright illumination when the power is applied can damage the sensitive cathode or conduct excessive current.

      4. Maintenance. Little maintenance is required unless the unit is subjected to extreme conditions of corrosion or temperature. Clean the optical unit with lens paper to avoid scratching.


    2. IONIZING RADIATION.

      1. Description and Applications. The ionizing radiation survey meter is useful for measuring radon decay products from air samples collected on filters. Wipe samples collected on a filter can also be counted with this detector, and general area sampling can be done. Several types of ionizing radiation meters are available from the CTC's loan program (ALEP).

        The survey meter with the scintillation detector can be used to measure the presence of radon-decay products in a dust sample. The barometric pressure should be noted for ionizing radiation chambers.

      2. Calibration. No field calibration is available. Periodic calibration by a laboratory is essential and should be handled by the CTC.


    3. NONIONIZING RADIATION.

      1. Description and Applications. Various nonionizing radiation survey meters are available through the CTC's ALEP for measuring electromagnetic fields. The frequency ranges covered by OSHA's instruments are: 10 Hz to 300 kHz, 0.5 MHz to 6000 MHz, 6 GHz to 40 GHz, and the 2.45 GHz microwave oven frequency. These instruments are capable of measuring the electric field strength (E-field), magnetic field strength (H-field), or both depending on the instrument.

        Depending on the instrument, electromagnetic field strengths from power lines, transformers, video display terminals, RF induction heaters, RF heat sealers, radio & television transmitters, microwave ovens and other sources can be measured.

      2. Calibration. No field calibration is available. Periodic calibration by a laboratory is essential and should be handled by the CTC.

      3. Special Considerations.

        a.  Some of the instruments have an automatic instrument zeroing, other instruments may require "zeroing" the instrument in a "zero-field" condition. Check the manual for guidance.

        b.  Some units have a peak memory-hold circuit that retains the highest reading in memory.

        c.  Some units operate with either electric (E) or magnetic (H) field probes based on diode-dipole antenna design. Total field strength is measured at the meter regardless of the field orientation or probe receiving angle. The diode-dipole antenna design of the probe is much more resistant to burnout from overload than the thermocouple design of probes used with other eters.

      4. Maintenance. No field maintenance is required other than replacing the alkaline batteries when needed.


  8. AIR VELOCITY MONITORS AND METERS.

    1. FLOW HOODS.

      1. Description and Applications. These instruments measure air velocities at air supply or exhaust outlets.

      2. Calibration. No field calibration is available. Periodic calibration by a laboratory is essential.

      3. Maintenance. These typically require little field maintenance other than battery-pack servicing and zero balancing of analog scales. (Check manufacturer's manual.)


    2. THERMOANEMOMETER.

      1. Description and Applications. These instruments monitor the effectiveness of ventilation by measuring air velocities.

      2. Calibration. No field calibration is available. Periodic calibration by a laboratory is essential.

      3. Maintenance. These typically require little field maintenance other than battery-pack servicing and zero balancing of analog scales. (Check manufacturer's manual.)


    3. 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.

  9. NOISE MONITORS AND METERS.

    1. SOUND LEVEL METERS.

      1. Description and Applications. The sound level meter is a lightweight instrument for the measurement of sound pressure level (SPL) in decibels. All ANSI-approved meters meet minimum requirements that include an A-weighted network, a slow-response meter characteristic, and a fully graduated scale with measurements ranging from 80 to 130 dBA. The Type II meter is most frequently used. Applications are in worker exposure and noise evaluations.

      2. Octave Band Analyzer. Some sound level meters may have an octave or one-third octave band filter attached or integrated into the instrument. The filters are used to analyze the frequency content of noise. They are also valuable for the calibration of audiometers and to determine the suitability of various types of noise control.

      3. Calibration. In normal operation, calibration of the instrument usually requires only checking. Prior to and immediately after taking measurements, it is a good practice to check, using a calibrator, the ability of the sound level instrument to correctly measure sound levels. As long as the sound level readout is within 0.2 dB of the known source, it is suggested that no adjustments to the calibration pot be made. If large fluctuations in the level occur (more than 1 dB), then either the calibrator or the instrument may have a problem.

      4. Special Considerations.

        a.  Always check the batteries prior to use. Use the microphone windscreen to protect the microphone when the wearer will be outdoors or in dusty or dirty areas. (The windscreen will not protect the microphone from rain or extreme humidity.)

        b.  Never use any other type of covering over the microphone (e.g., plastic bag or plastic wrap) to protect it from moisture. These materials will distort the noise pickup, and the readings will be invalid.

        c.  Never try to clean a microphone, particularly with compressed air, since damage is likely to result. Although dirt and exposure will damage microphones, regular use of an acoustical calibrator will detect such damage so that the microphones can be replaced.

        d.  Remove the batteries from any meter that will be stored for more than 5 days. Protect meters from extreme heat and humidity.

      5. Maintenance. No field maintenance is required other than replacement of batteries.


    2. PERSONAL DOSIMETERS.

      1. Description and Applications. These meters can be worn by personnel to obtain individual readings of noise exposure. Typical dosimeters consist of a pocket-sized monitor with remote microphone and an indicator for readout of exposure data. Some have a preset threshold; others have a selector switch that may be preset. It is also possible to select the threshold, criterion level, and exchange rate on many dosimeters.

      2. Calibration. Field calibrate at the measurement site according to the manufacturer's instructions both before and after each use. Use an acoustical calibrator that was designed to be used with the particular model noise dosimeter being used.

      3. Special Considerations.

        a.  Always check the batteries prior to use. Be very careful with the microphone cable. Never kink, stretch, pinch, or otherwise damage the cable.

        b.  Use the microphone windscreen to protect the microphone when the wearer will be outdoors or in dusty or dirty areas. (The windscreen will not protect the microphone from rain or extreme humidity.)

        c.  Never use any type of covering over the microphone (e.g., plastic bag or plastic wrap) to protect it from moisture. Such materials will distort the noise pickup, and the readings will be invalid.

        d.  Never try to clean a microphone, particularly with compressed air, since damage is likely to result. Although dirt and exposure to industrial environments will damage the microphones, regular use of an acoustical calibrator will detect such damage so that microphones can be replaced.

        e.  Remove the batteries when the dosimeter will be stored for more than 5 days. Protect dosimeters from extreme heat and humidity.

      4. Maintenance. No field maintenance is required other than replacement of batteries.

  10. ELECTRONIC TESTING METERS.

    1. DESCRIPTION AND APPLICATIONS. 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.

    2. CALIBRATION. Few, if any, field calibrations are available. Check manufacturer's manual. Periodic calibration is to be handled by the CTC.

    3. MAINTENANCE. No field maintenance is required other than battery-pack servicing.


  11. HEAT STRESS INSTRUMENTS.

    1. DESCRIPTION AND APPLICATIONS. Heat-stress monitors are portable instruments used to measure environmental factors that may cause heat-related injuries. Personal heat-stress monitors measure body temperature and sometimes heartbeat through sensor belts around the chest or ear-canal sensors.

    2. CALIBRATION. Most calibration is done by a laboratory.

    3. MAINTENANCE. Some field servicing is required (check manufacturer's manual).


  12. BIBLIOGRAPHY.


A.M. Best Co. (AMB). 1990. Bests Safety Directory. AMB: Odwick, NJ.

Hering, S.V., Ed. 1989. Air Sampling Instruments for Evaluation of Atmospheric Contaminants. American Conference of Governmental Industrial Hygienists: Cincinnati, Ohio.



APPENDIX II:3-1. CALIBRATION INTERVALS.

The information below is for general reference only. Calibration or servicing due dates are shown on the equipment. Contact the CTC for specific information.

TABLE II:3-1. CALIBRATION INTERVALS
Instrument
 Interval (years)
Air Sampling Pumps *
Air Sampling Pump Calibrators 1
Air Velocity Meters 2
Battery Chargers *
Distance/Range Finders
      Electronic Distance Meters		 *
1
Dust Monitors 1
Electrical Testers
      GFCI Testers
      Multimeters
      Tic Tracers		 1
2
2
*
Ergonomics
      Force Gauge Meter		  
2
Gas Monitors
      National Draeger Model 190 & PAC III
      BioSystems Toxi Plus & Ultra, CO H2S		 1
2
2
Heat Stress Monitors 1
Ionizing radiation 1
Light Meters 2
Nonionizing radiation meters 1
Pressure gauges 2
Respirators
      Powered Air Purifying
      Fit Testers		  
1
1
Sound Instruments
      General Purpose (Type 2)		 1
  1*
Stop Time Meters 1
Tachometers 1
Vibration Meters 1
*  =  Field Inspect/Send to the CTC for repair only


APPENDIX II:3-2. GENERAL PROCEDURES FOR RETURNING INSTRUMENTS TO CTC.

Note:   Never use a carrying case like a shipping case. Carrying cases should be carefully stuffed to avoid any instrument movement during shipping and securely packed in a cardboard box.

Simpson 260 Multimeter:   Pack extra carefully, as they are extremely susceptible to damage during shipping.

All Hot Wire Anemometers:   Return with their probes. Instrument and probe serial numbers are usually the same.

Heat Stress Monitors:   Send all associated probes and accessories.

Air Sampling Pumps:   Return with battery packs. Several types of battery packs can be repaired. If instrument is shipped with batteries or battery pack inside, turn off all switches.

Remove all batteries from sound measuring instruments (do not send batteries with the instrument).

GenRad 1982 Sound Level Meter and Analyzer:   Send all associated attenuators and pre-amplifiers with the instruments.

Any instrument with gauges, meters, glass or plastic parts exposed should have special protection over or around these parts before final packing for shipment. If a case has been furnished with the instrument, the case should be used whenever the instrument is not actually being operated. The case provides necessary protection. Styrofoam packing, bubbled polyethylene film, or crumpled newspaper may be used for packing.

Those instruments not specifically listed should be shipped using the customary precautions. Contact CTC if you have questions about specific instruments.


APPENDIX II:3-3. 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 (ALEP) or through the SLTC.

TABLE II:3-2. 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
Multimeters 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 gauges Air pressure compressor air lines
Pumps, low Air volume sampling with charcoal 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



TABLE II:3-3. GAS & VAPOR METERS
Type of instrument
Measured substance
Application
Double-range meters Combustible gas, O2 confined spaces
Triple range meters Toxic, O2, combustible gas confined spaces
Quad range meters 2 toxics, O2, combustible gas  
CO dosimeter CO garages, indoor air quality
Carbon dioxide meter CO2 indoor air quality
Infrared analyzers CO, CO2, organic substances traces indoor air, leaks, spills
Hydrogen cyanide monitors Hydrogen cyanide plants
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



TABLE II:3-4. 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, VDT'S, induction motors



TABLE II:3-5. BIOLOGICAL MONITORS
Type of instrument
Measured substance
Application
Microbial sampler Microbes indoor air quality



 
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