about the various toxic gases found in and around agricultural
buildings (especially silos, manure pits, and grain bins) and
what precautions should be taken to minimize exposure to and/or
damage done by these hazardous gases. Also to identify the specific
kinds of protective equipment needed when working in confined
spaces and the differences in respiratory protective equipment.
respirator, powered air purifier, gas mask, air supplied respirator.
toxic gases of major concern can be found in manure pits
and silos. They are: Hydrogen sulfide (H2S),
ammonia (NH3), carbon dioxide (CO2),
methane (CH4), and nitrogen dioxide (NO2).
primary hazards of these gases are:
or poisonous reactions in people or animals
depletion which can result in asphyxiation
that can occur when oxygen mixes with the gases (primarily
a problem with methane)
of hydrogen sulfide (H2S)
dangerous gas associated with waste decomposition
rotten egg smell
breathing this gas a short time, sense of smell becomes
fatigued and you can no longer detect an odor
low concentrations H2S irritates the eyes
and respiratory tract; at moderate levels exposure causes
headache, nausea, and dizziness; at high concentrations
H2S causes death
of ammonia (NH3)
sharp, penetrating odor detectable at very low concentrations
moderate levels of concentration, can irritate eyes
and respiratory tract; at high concentrations can cause
ulceration to the eyes and severe irritation to the
of carbon dioxide (CO2)
heavier than air, difficult to detect
oxygen in air and acts as an asphyxiant
moderate concentrations causes shortness of breath and
major contributing factor to animal deaths by asphyxiation
in confinement buildings with faulty ventilation
of methane (CH4)
and lighter than air, so it tends to accumulate at the
top of manure pits
an asphyxiant at extremely high concentrations. Main
hazard is its flammable, explosive nature
of nitrogen dioxide (NO2)
sweetish odor, even at low concentrations. Has reddish-brown
color, visible only in extremely high concentrations
than air and can settle at the bottom of enclosed spaces
of the most hazardous lung irritants, however, the effect
is so subtle that the victim may not realize the serious
nature of the exposure until it is too late. Can cause
bronchitis, chemical pneumonia, a severe fibrosis-type
of pneumonia, severe lung damage than can be fatal in
two to 10 days; or acute pulmonary edema that can be
fatal in less than 48 hours.
working in agricultural buildings provide as much ventilation
as possible, especially around manure pits during the agitation
of waste. No workers should be near a manure pit or
in the building during the agitation process. If possible,
remove all animals from the building.
entering a manure pit at any time, it at all possible.
Even if the pit has been emptied, it still may be lacking
in oxygen or have high concentrations of toxic gases.
keep at least one toot of space between the highest manure
level and the slats. This protects animals who lie on
the slats and inhale the gases that accumulate at the surface
of the pit.
not allow anyone to enter a silo during the tilling process
until the blower has run for at least 30 minutes.
enter a silo or manure pit area without someone on the outside
monitoring your activity.
not allow anyone to enter a silo for seven to 10 days after
the filling process is complete because the fermentation
process produces toxic gases.
the specific type of respiratory protective equipment necessary
for the hazards present and the amount of filtering necessary.
Regardless of the type that is chosen, however, all respiratory
protection must be approved by the National Institute for
Occupational Safety and Health (NIOSH).
purifying respirators remove contaminants from the air,
but can be used only in an environment that has enough oxygen
to sustain life. Do not use air purifiers to provide
protection from the dangers of oxygen-limited environments.
There are two general types of air purifying respirators;
those with mechanical filters and those with a chemical
cartridge. Mechanical filter purifiers are not for use around
toxic gases.~ Chemical Cartridge respirators protect against
certain gases and all but the most toxic organic vapors.
air purifiers can be mechanical filter, chemical cartridge,
or a combination of both. They cannot be used in oxygen-limited
masks are more effective than chemical cartridge respirators
against high concentrations of toxic gases. Gas masks
should not be used in oxygen-limited environments.
respirators are for use in oxygen-deficient areas such as
manure pits, silos containing silo gas, airtight silos,
or bins containing high moisture grain. The two main
types of supplied-air respirators are the hose mask with
blower and emergency air supply, and the self-contained
breathing apparatus (SCBA).
State University Cooperative Extension Service, Manhattan, Kansas.
KSU Cooperative Extension Service provides practical, research-based
information and educational programs to address critical issues
facing individuals, families, farms, businesses and communities.
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.