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Jeff
Lorimor, Charles
V. Schwab and Laura
Miller
Iowa State University Extension
Gases
and odors may be a nuisance for many livestock producers,
but they also can be a life-threatening danger when confined
to buildings or manure pits.
Every
year in Iowa, incidents are reported in which someone is overcome
by deadly manure gases. These incidents have resulted in several
deaths and many more illnesses caused by exposure to poisonous
gases. This does not include economic losses from animals
that die from the gases.
It is
difficult to know when air quality problems will occur. The
best precaution is to understand the sources of air quality
problems, and what to do to reduce or eliminate them. This
publication will discuss five common gases found in manure
storage facilities, and other hidden dangers.
Gases
are generated as animal wastes break down. Gas builds over time,
often rising to the surface and escaping into the air. Enclosed
livestock areas must be ventilated, even on cold winter days,
to remove moisture and gases. When ventilation rates fall below
a minimum, or when conditions increase the release of gas to
the air (such as pit agitation), serious problems can occur.
- Carbon
dioxide is the result of animal respiration. Carbon
monoxide is the result of using combustion equipment,
such as heaters and gas-operated power washers, in a confined
area. This equipment produces more carbon monoxide when
engines don't burn cleanly.
At high concentrations, carbon dioxide and carbon monoxide
can cause respiratory distress and headaches. At prolonged
high exposures, these gases can be fatal. Federal standards
set maximum concentrations at 5,000 parts per million
(ppm), about 0.5 percent, for carbon dioxide; and 50 ppm,
about 0.005 percent, for carbon monoxide.
Solution:
These gases usually aren't a problem under normal conditions
with proper ventilation. However, it's important to maintain
some ventilation at all times, even when animals are not
present.
- Ammonia
is a troublesome by-product of manure decomposition. It
is an eye irritant at levels above 20 to 25 ppm. When exposed
to levels around 1,500 ppm, people begin to cough and froth
at the mouth. Ammonia is deadly at 5,000 ppm.
Ammonia has a distinct odor, which humans can detect in
concentrations as small as 5 ppm. It's common during winter
months for ammonia levels to exceed 25 ppm, even under
normal winter ventilation rates. Although it is debated
by safety experts, 25 ppm is frequently recommended as
a maximum acceptable level for ammonia. If your eyes burn
when you enter an enclosed livestock facility, you know
ammonia levels are at least 20 ppm.
Solution:
Provide at least a minimum winter ventilation rate throughout
the year. Water attracts ammonia, so frequent rinsing
of equipment or leaving at least a half-inch of water
in pits or on the floor can help.
- Methane
is dangerous because it is highly combustible. At concentrations
of 50,000 ppm or more (a level of 5 percent), methane can
explode. Methane gas is produced as animal wastes decompose,
and warm temperatures accelerate this process. Another problem
is that this colorless, odorless, tasteless gas is difficult
to detect. Methane is lighter than air and will accumulate
in the top of unvented areas, such as closed pits. The maximum
allowable concentration is 1,000 ppm, or 0.1 percent.
Solution:
Make sure all pits and manure storage areas are adequately
ventilated. Prohibit all open sparks or flames in areas
near pits or storage facilities.
- Hydrogen
sulfide is the most dangerous gas found in enclosed
livestock operations. It is responsible for most manure-related
deaths of animals and people.
Within seconds of exposure, hydrogen sulfide can cause
unconsciousness, which can be fatal. Concentrations as
low as 1,000 ppm can result in death. The maximum allowable
concentration is 10 ppm.
Hydrogen sulfide is heavier than air, so it will accumulate
in underground pits or other low-lying, unventilated areas.
Although its rotten egg odor can be detected at levels
of less than 1 ppm, the gas will paralyze the sense of
smell at higher levels.
Solution:
Whenever you work in manure storage facilities, always
assume hydrogen sulfide is present. Follow these safety
precautions to minimize the dangers of hydrogen sulfide:
- Provide
extra ventilation during agitation.
- Never
enter a pit without precautions.
- If
you suspect high hydrogen sulfide levels for any reason,
leave the building immediately. Signs include the presence
of sick or dead animals in the area, or a sudden headache
or dizziness.
The
large volume of liquid that must be stored in many manure systems
is also a danger. Children and adults can drown in pits, commonly
as deep as 8 feet. Pits typically have either very steep or
vertical walls, making escape almost impossible.
Pits
are inaccessible if they're covered by slats, and outdoor
pits with concrete lids pose few dangers to bystanders or
workers. However, the cost of covering pits and the larger
size of pits in recent years has lead to increasing use of
open pits, both earthen and concrete. Without protection,
such as high fences and locked gates, open pits are potential
hazards.
Another
problem may be push-off ramps used in some dairy operations.
A strong safety cable at the end of the ramp may prevent a
machine from falling into the pit. Beef and dairy pits also
may form unstable crusts that can get covered with weeds.
Never
try to rescue someone who is unconscious in a manure storage
structure unless you have the proper equipment and knowledge
of the situation. Multiple deaths are common because rescuers
succumb to the same gases as the victim.
The
immediate response should be to contact an ambulance or local
emergency medical services. You may attempt a rescue if you
are wearing a self-contained breathing apparatus, have a rescue
line, and have another person at the end of the line to help.
Toxic
odors and gases are natural by-products of all livestock operations.
Persons who work in these environments must know that air
quality problems can develop at any time. However, a cautious
attitude and proper equipment can help you avoid a life-threatening
situation.
How
Much Do You Know?
- Which
manure gases can you readily smell?
- ammonia
- hydrogen
sulfide
- carbon
dioxide
- How
deep are most manure pits?
- 4
ft.
- 8
ft.
- 12
ft.
- The
ammonia level is at least 20 parts per million (ppm) if
your eyes burn. True or false?
- How
much hydrogen sulfide can be fatal?
- 10
ppm
- 100
ppm
- 1,000
ppm
- If
you're pumping out a deep pit in a building and notice dead
hogs, what could be the cause?
- exposure
to methane
- exposure
to hydrogen sulfide
- exposure
to ammonia
- When
someone is overcome by manure gases, try to get that person
out as quickly as possible. True or false?
See
answers at the end of "What Can You Do?".
What
Can You Do?
- Learn
the danger signs of toxic levels of manure gases.
- Post
warning signs around manure pits and enclosed livestock
facilities about the possibility of a contaminated atmosphere.
- Inquire
about the rescue equipment available from your local emergency
response team to handle gases that could be present in your
operation.
- Maintain
a fence around open pits and keep the gate locked at all
times.
- Keep
the area around earthen pits mowed and free of tall weeds.
- Never
enter a manure pit alone.
Answers
to quiz:
1-a
and b; 2-b; 3-True; 4-c; 5-b; 6-False.
- For
regulations regarding manure pits or livestock storage facilities,
contact the Iowa Department of Natural Resources (DNR) or
your local extension office.
- For
details about manure gases and their prevention, contact
your local extension office for a copy of the Midwest Plan
Service's Waste Facilities Handbook, MWPS-18. This is a
fee publication.
- For
technical information about exposure to manure gas, contact
the Technical Information at the National Institute for
Occupational Safety and Health (NIOSH) by calling, toll-free,
1-800-35-NIOSH.
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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
This document is Fact Sheet
Pm-1518k
, a series of the Safe Farm Program, Iowa State University Extension,
Ames, Iowa. Safe Farm promotes health and safety in agriculture.
It is funded by the National Institute for Occupational Safety
and Health, Iowa State University, and a network of groups that
serve Iowa farm workers and their families. Publication date:
November 1993.
Jeff
Lorimor, extension engineer; Charles V. Schwab, extension
safety specialist, and Laura Miller, extension communications,
Iowa State University Extension, Ames, Iowa.
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