Howard
J. Doss and Cornita
Tilma
Michigan State University Extension
Today's
modern farming methods have brought new dangers that arise
from farmers entering confined areas where oxygen levels may
be inadequate or where toxic gases are present. When entering
a confined area such as a manure pit, silo, grain bin, or
an inadequately ventilated building a farmer may be at risk
of being overcome by gases or dusts which can cause permanent
lung damage or death.
Gases
in manure pits and silos can quickly kill an unsuspecting
farmer or an untrained rescue worker who enters the area without
adequate protective equipment. Farmers entering grain bins
while the bin is being emptied may be taking an unnecessary
risk of being crushed or suffocated by flowing grain. Working
in grain bins without proper respiratory equipment to filter
dusts and molds increases a farmer's chances of developing
a respiratory disease. Farmers working in dust-laden buildings
run the risk of developing Farmer's Lung, a disease that permanently
damages lung functions.
While
most farmers are aware of the dangers of poisonous gases and
flowing grain hazards, statistics from the past four years
show that three to five Michigan farmers are killed each year
in accidents involving these hazards. The occurrence of respiratory
diseases among farmers cannot be accurately measured, but
they are a concern among the rural population.
The
intent of this publication is to make the reader aware of
the risks associated with entering a confined space area and
to provide information about risk reduction techniques for
farm and orchard owners.
There
are several gases around farm sites that pose a risk to farmers,
the three most common in confined space areas are hydrogen sulfide,
ammonia and carbon dioxide.
Hydrogen
sulfide (H2S) is formed during manure decomposition.
It is toxic, combustible, and because it is heavier than air,
it dissipates oxygen and can suffocate an unsuspecting farmer.
Hydrogen sulfide also has a distinctive "rotten egg" stench
that dulls the sense of smell, giving the farmer a false sense
of security because the original odor disappears as exposure
time increases. The gas irritates the eyes and respiratory
tract. In low concentrations, hydrogen sulfide has been reported
to cause headaches, nausea and dizziness prior to the individual
succumbing to the gas.
Ammonia
(NH3) is a suffocant and a toxic gas with a distinct,
sharp penetrating odor. Prolonged exposure to ammonia, or
exposure to high concentrations of the gas can cause ulceration
of the eyes and severe irritation to the respiratory system.
Carbon
dioxide (CO2) is a colorless, odorless suffocant
that is produced during decomposition and respiration of plant
materials. Excess carbon dioxide in a confined space depletes
oxygen levels needed to sustain life. At low levels (CO2
levels at 3 to 6 percent) the individual may feel drowsy and
develop a headache. Death from suffocation may result when
carbon dioxide levels are 30 percent or greater.
Dusts
are a common hazard in farming. All dusts have the potential
to cause health problems, but some organic or toxic dusts may
permanently impair a farmer's health.
The
type of dust, amount and duration of exposure will determine
the degree of severity of the health problem. Some dusts,
especially dust from moldy forage, grain, or hay, carries
antigens that can cause severe irritation to the respiratory
tract. Breathing dust from moldy feed materials can result
in a permanent lung condition commonly known as "Farmer's
Lung".
Farmer's
Lung is one of the most disabling diseases among dairy farmers.
Symptoms of Farmer's Lung are easily mistaken for bronchitis
or pneumonia and may not be noticed for several hours after
exposure to the dust. Irreversible lung damage and sometimes
death results when the disease is not diagnosed and treated
in early stages. A long-term implication of the disease is
shortness of breath which requires the farmer to take frequent
rest periods and severely limits the amount of work that can
be accomplish.
"Nuisance
dust" is a term frequently applied to less noxious forms of
dust that a farmer is commonly exposed to while performing
field operations or working around livestock. Inhaling these
less noxious dusts decreases lung capacity and also causes
some people to be more susceptible to respiratory infections
such as pneumonia. Prolonged inhalation of dusty air causes
lungs to harden and become inelastic; significantly reducing
their functional capacity. Smoking of tobacco products has
been reported to hasten the damage.
Prevention To reduce
the risk of respiratory problems from dusts, a farmer should
store only dry grain and dry, well-cured forages and hay. Mold
develops in moist or wet grain, forages, hay and many other
moist or stale organic materials.
To reduce
dust exposure, a farmer should keep animal areas as clean
and dust-free as possible. Stale dust and feed accumulations
attract and absorb moisture from the air in the barn, creating
an environment for mold and other microorganisms to grow.
Safety
Precautions
- Disposable
dust masks or a respirator with a replaceable cartridge
designed to filter dusts ensures an adequate supply of clean
air for the farmer. Change the mask or cartridge frequently
for the greatest protection.
- Filter
masks may provide adequate protection from common agricultural
molds, dusts, and chaffs; however, they will not protect
the wearer from agricultural gases. A self-contained breathing
apparatus similar to those worn by fire fighters is needed
to work in oxygen deficient areas such as silos or manure
pits (see Figure 1).
(Agricultural
operations with employees should refer to Michigan Department
of Labor and Michigan Department of Public Health standards
concerning confined spaces and potentially toxic work environments.)
To reduce
the risks associated with working in a confined space, farmers
should:
- Never
enter a confined space without ventilating the area.
- Test
the atmosphere if possible.
- Wear
a correctly fitted, approved, self-contained breathing apparatus
if the area cannot be ventilated or properly checked. In
addition, a safety harness and lifeline should be used.
- A
self-contained breathing apparatus may fail or the worker
could be trapped when working in a confined space with toxic
gases. To reduce the risk to the person entering a confined
space, two people should be available to assist in an emergency
rescue. At least one person should be equipped with appropriate
breathing equipment to execute the rescue.
- Have
ladders, ropes and lifts available to assist a person entering
a confined space and for rescue efforts if entrapment is
possible or if gas fumes may be present.
- Maintain
communication with the individual(s) outside the confined
space. Communication may be visual, vocal, and/or by signal
line.
- All
persons who enter or may enter hazardous confined spaces
should be trained in the use of safety equipment. A self-contained
breathing apparatus should be properly fitted. The smallest
leak could be deadly.
Michigan
Department of Labor Safety Standards provide strict requirements
when employees are required to enter hazardous spaces or confined
spaces that test hazardous. Instruction must include information
about the nature of the hazards involved, the necessary precautions
to be taken, and the correct use of required protective and
emergency equipment.
Grain
flow is a potentially deadly entrapment that may crush or
suffocate anyone caught in the flowing grain. Accidents can
occur when someone enters a bin to dislodge a bridge of grain
that forms over the auger and stops grain flow. It takes only
3 to 4 seconds for a person to become entrapped in flowing
grain; an average adult can become completely submerged in
less than 20 seconds (see Figure 2).
Safety
Precautions
- Stay
out of grain bins, wagons and grain trucks when unloading
equipment is running.
- If
it is necessary to enter the bin, remember to shut off the
unloader. It is a good idea to lock out any unloading equipment
before you enter a bin to prevent someone from unintentionally
starting the equipment while you are in the bin.
- Children
should not be allowed to play in or around grain bins, wagons,
or truck beds.
- Ladders
and ropes should be installed inside grain bins to provide
a grabhold or for an emergency exit. Attach ropes to the
ladders and from the top center of the bin. Anyone entering
the bin should attach a rope and harness to themselves before
entering the bin. Ladders are easier to locate inside a
dusty bin if there are brightly painted stripes just above
or behind the ladder.
The
Michigan Department of Labor Standards for Personal Protective
Equipment requires employees to wear a safety belt or a safety
harness and a lanyard affixed by a rope grab to a lifeline.
All components must meet the state requirements. The Michigan
Occupational Safety and Health Administration (MIOSHA) requires
a lift tripod and harness lifeline arrangement for a rescue
from the grain bin.
Remember
that crusted grain may be covering voids or cavities that
can entrap you. If possible, break up crusted grain from the
outside of the bin with a long pole (see Figure 3).
If you
must enter the bin:
- Wear
a harness attached to a rope.
- Stay
near the outer wall of the bin and keep walking if the grain
should start to flow.
- Have
another person, preferably two people, outside the bin who
can help if you become entrapped. These people should be
trained in rescue procedures and should know and follow
safety procedures for entering the confined space.
- Grain
fines and dust may cause difficulty in breathing. Anyone
working in a grain bin, especially for the purpose of cleaning
the bin, should wear an appropriate dust filter or filter
respirator.
Several
hazards exist when a person is required to enter a filled or
partially-filled upright concrete or oxygen-limiting silo. Several
different gases are produced during the ensilage process and
as forages undergo fermentation.
The most dangerous gas produced in the fermentation process
is nitric oxide which, when combined with oxygen, produces
nitrogen dioxide commonly referred to as "silo gas" (see Figure
4). In high concentrations, silo gas can kill a farmer after
a short exposure.
A strong
bleach-like odor or a yellowish or reddish cloud on top of
freshly ensiled materials may be an indication that silo gas
is present. Dead birds or insects around the base of the silo
is another sign that silo gas may be present. But there may
be no visual signs or no distinct odor to warn a person of
silo gas.
Seek
medical attention immediately if you suspect that you have
been exposed to silo gas. Many times there is a symptom-free
period of « to 42 hours after exposure until the onset of
health problems. An acute onset of shortness of breath and/or
fever and lung infiltrates are symptoms of silo-filler's disease.
Frequently there is a relapse of the disease 2 to 6 weeks
after the initial symptoms.
Safety
Precautions
- Do
not enter the silo for 4 to 6 weeks after filling stops.
- Be
alert for silo gas odors and/or yellowish-brown or reddish
fumes in or near the silo.
- Silo
gas is heavier than air and will displace oxygen. Wear a
self-contained breathing apparatus if you must enter the
silo during the first 4 to 6 weeks after filling stops.
Regular respirators or dust masks will not protect you from
the gas.
- Running
the silo blower for 15 to 45 minutes before entering the
silo and while you are in the silo will help remove silo
gas, but this is not a substitute for a self-contained breathing
apparatus if silo gas is suspected.
- Never
enter a silo if you are alone, especially during the danger
period when gases may still be forming.
- Get
to fresh air immediately if you start coughing or experience
throat irritation.
- Seek
medical attention if you suspect you have been exposed to
silo gas.
- During
the dangerous loading and fermentation period provide fencing
around the silo base to keep children and animals a safe
distance away from toxic silo gases. There have been reports
of livestock being killed from silo gas flowing down the
chute and entering the barn.
- Provide
good ventilation to the silo room to dissipate dense gases
as they cascade out of the silo during fermentation.
- If
the silo adjoins a barn (or other building), keep the door
between the two structures closed to prevent gas escaping
into the livestock area.
Controlled
atmosphere storages have high levels of carbon dioxide (CO2)
and low levels of oxygen (O2) as compared to normal
air, which contains 0.035 to 0.04 percent carbon dioxide. Controlled
atmosphere storages commonly contain 2 to 5 percent CO
2,
a deadly level for human beings. Oxygen levels inside these
types of storage facilities ranges from 2.5 to 3 percent,
well below the "required" human level of about 21 percent.
Anyone
entering a controlled atmosphere room must wear a self-contained
breathing apparatus or a supplied-air respirator if the oxygen
level is below 17 percent. If possible, open the room to provide
thorough ventilation if entry is necessary. The controlled
atmosphere can generally be quickly re-established before
stored fruit is damaged.
Another
safety consideration for CA storages relates to the combustion
units used for artificially creating and maintaining the low
oxygen atmosphere. Combustion generators can be potentially
hazardous and must be operated according to instructions.
When incomplete combustion takes place, toxic gases are produced
which will harm the fruit as well as people. The toxic gases
resulting from incomplete combustion could accumulate in the
storage room in explosive concentrations.
Gases
such as hydrogen sulfide (H2S), ammonia (NH3),
carbon dioxide (CO2) and methane (CH4)
are a major concern in manure pits.
Manure
pits provide a deceptive hazard. Many pits are semi-open vats,
but because many deadly gases are heavier than air they remain
in the pit at lethal concentrations.
Adequate
ventilation and/or air circulation must be provided before
a manure pit is entered. Ventilation and air circulation is
also important if the pit is sufficiently close to buildings
where livestock are housed or where humans enter.
Open
flames or smoking in the area of many gases, especially around
highly explosive methane gas, can be deadly.
- Provide
adequate ventilation during agitation of pit contents.
- Provide
backup power for mechanical ventilation in case of power
failure. Also, provide for equipment backup if any part
of the ventilating system should fail.
- Be
sure that humans and livestock are not inside confinement
buildings during agitation.
- Always
keep at least 12 inches of clear space between the highest
manure level and the floor slats.
- Never
enter a manure pit without wearing a self-contained breathing
apparatus. There are potentially fatal gases in pits, even
after the pit has been emptied.
NEVER
enter a manure pit without:
- a
self-contained breathing apparatus,
- a
lifeline and harness with adequate retrieval equipment (hoist,
etc.), and
- sufficient
personnel standing by to effect a "safe" rescue. Rescue
personnel should be equipped with a complete self-contained
breathing apparatus and trained in rescue procedures. There
has been at least one instance where rescue workers were
killed when they entered a pit without proper protection.
- Michigan
Department of Labor
- Michigan
Department of Public Health
- John
Deere Agricultural Safety (FMO Series)
- Illustrations
courtesy of John Deere and Company, Agricultural Safety,
Fundamentals of Farm Safety, 1987.
Agricultural
operations with employees should be familiar with and
follow procedures established for an employee(s) working in
a confined space (i.e. manure pits, upright silos, grain bins,
controlled atmosphere storages, etc.).
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
Michigan
State University, Agricultural Engineering Department.
Howard
J. Doss and Cornita Tilma, Agricultural Safety Specialist
and former Graduate research assistant respectively, Michigan
State University Extension, East Lansing, Michigan 48824.
5/92. Funded by the National Institute of Occupational Safety
and Health -
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