HOUSING PIH-104
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Safety in Swine Production Systems
Authors:
James Barker, North Carolina State University
Stanley Curtis, University of Illinois
Ordie Hogsett, University of Illinois
Frank Humenik, North Carolina State University
Reviewers:
Kelley Donham, University of Iowa
Ken Kreig, University of Alaska
John Sweeten, Texas A&M University
Introduction
The swine industry has increasingly moved toward specializa-
tion and mechanization for high density rearing of livestock. One
aspect of this specialization can be seen in housing systems that
assist managers in raising animals with less labor in a more con-
trolled environment, one that incorporates mechanized ventila-
tion, supplemental heating, liquid or slurry manure handling, and
automated dry-feed handling. These systems introduce new manage-
ment factors related to both people and livestock. It is signifi-
cant that animal health and performance advantages of housing
systems when compared to pasture or dirt lot systems are
reflected in lower mortality, better feed conversion, and
increased growth rates.
However, manure accumulations within enclosed buildings gen-
erate gases which can be both toxic and asphyxiating when improp-
erly managed. Another problem is unvented heaters in poorly ven-
tilated buildings that lack enough oxygen for complete fuel
combustion. This situation can increase carbon monoxide levels.
Dust resulting from automated feeding systems, animal hair and
dander, and dried manure on floors and animals can irritate
respiratory systems. The severity of these problems is seasonal
in that the atmosphere within enclosed buildings is often much
better during the summer than the winter because ventilation
rates are not reduced for heat energy conservation.
The potential danger of stored manure gases must be
respected. Livestock have died as a result of ventilation
failures or stored manure agitation. Human fatalities have
occurred from entering a manure collection or storage pit without
insuring adequate ventilation or without being equipped with
proper breathing apparatus. In addition, manure storage pits or
tanks and lagoons, like any water impoundment, should be
respected for the drowning potential.
Toxic and Asphyxiating Gases
When manure and urine are stored and undergo anaerobic
digestion, dangerous gases are produced. The ones of primary con-
cern are: hydrogen sulfide, ammonia, carbon dioxide, and methane.
But more than 40 different gases are produced; and some, such as
volatile acids, amines, and mercaptans are highly odorous in very
small quantities. In addition, carbon monoxide can rise to toxic
levels when heating units malfunction or inadequate oxygen is
present.
Hydrogen Sulfide (H2S). Hydrogen sulfide is the most toxic
gas associated with the decomposition of swine manure. It is
believed to have been responsible for most of the deaths of
livestock and humans that have occurred around liquid manure
storage pits. It is colorless, heavier than air, and highly solu-
ble in water; it has the characteristic odor of rotten eggs.
However, the odor of hydrogen sulfide can be deceiving. It is
first detected, by most people, at concentrations below one part
per million (ppm) by volume. (One ppm is the equivalent of one
volume of gas mixed in one million volumes of air.) Above 6 ppm,
the odor will only increase slightly even though the concentra-
tion of hydrogen sulfide increases significantly. The gas at 150
ppm can have a deadening effect on the sense of smell making
detection extremely difficult.
A common level of hydrogen sulfide gas in environmentally
controlled swine units is around 5 ppm. But during the first
stages of stored manure agitation and pumping liquid manure,
hydrogen sulfide can reach dangerous concentrations. Levels of
200 to 300 ppm have been reported to exist within a few minutes
after agitation begins, and levels can go as high as 1,500 ppm.
The effects hydrogen sulfide can have on humans and swine, at
different levels, are shown in Table 1.
The National Institute of Occupational Safety and Health
(NIOSH) maximum recommended safe concentration of hydrogen sul-
fide for workers in a building during an eight-hour work period
five days per week is 10 ppm. Human evacuation is recommended
when levels exceed 50 ppm.
Even if a person does not lose consciousness after inhaling
heavy doses of hydrogen sulfide, medical attention still should
be sought since fluids can accumulate in the lungs following
exposure.
Ammonia (NH3). During storage and decomposition, signifi-
cant amounts of ammonia are released from manure and urine.
Sources of ammonia include urine and feces on the top of slats or
solid floors and in the pit. Ammonia gas is an irritant which is
colorless, lighter than air, and highly water soluble. It has a
sharp pungent odor that becomes detectable at levels as low as 5
ppm.
Typical ammonia levels in well-ventilated environmentally
regulated buildings are 10-20 ppm with liquid manure systems and
50 ppm where manure and urine are deposited on solid floors. Lev-
els can exceed 50 ppm with lower winter ventilation rates and
reach 100-200 ppm in poorly ventilated buildings. The effects of
exposure to ammonia gas are presented in Table 2. The NIOSH max-
imum recommended safe ammonia concentration for workers in a
building for an eight-hour work period is 25 ppm.
Carbon Dioxide (CO2). The earth's atmosphere normally con-
tains 300 ppm of carbon dioxide. At considerably higher concen-
trations, it can asphyxiate people by reducing the amount of oxy-
gen present.
Manure decomposition and the normal breathing process of
animals can increase the level of carbon dioxide in confined
spaces. Typical concentrations inside ventilated buildings range
from 1,000 ppm during well-ventilated periods to 10,000 ppm dur-
ing winter. The effects of excessive concentrations of carbon
dioxide are presented in Table 3. The NIOSH maximum recommended
safe carbon dioxide concentration for workers is 5,000 ppm.
Methane (CH4). Methane is produced during natural decompo-
sition of manure and is nontoxic. It is rarely a problem in swine
buildings. However, high concentrations can cause headaches and
even asphyxiation. The major safety concern about methane is that
it is highly flammable and can be explosive at levels ranging
from 50,000 to 150,000 ppm (5 to 15 percent). Because methane is
lighter than air, it tends to rise and accumulate near the higher
stagnant parts of enclosed buildings and tightly closed manure
storage pits. This colorless, odorless gas is only slightly solu-
ble in water. But if a unit is well-ventilated, concentrations
should be well below the minimum explosive point.
The NIOSH maximum recommended safe methane concentration for
workers during an eight-hour period is 1,000 ppm. Its effects on
humans and swine are presented in Table 4.
Carbon monoxide (CO). When fuels burn incompletely, as all
fuels do to some extent, carbon monoxide is produced. This is a
gas which is most notorious for killing people who operate their
car engines inside closed garages.
Inside a building, carbon monoxide can build up in poorly
ventilated areas where heating units malfunction, where there are
unvented heaters, or where there are gas catalytic heaters.
closed and ventilation rates are lowest. A victim can be unaware
of the presence of carbon monoxide because it is colorless and
odorless. The NIOSH maximum recommended safe working carbon
monoxide concentration for adults during an eight-hour period is
50 ppm. Pregnant female workers should be aware that an unborn
fetus is more susceptible to carbon monoxide than adults. Carbon
monoxide has the same density as air and is insoluble in water.
Table 5 presents the effects of carbon monoxide exposure.
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| |
|Table 1. Effects of hydrogen sulfide exposure on humans and |
|swine. |
| |
|_________________________________________________________________ |
|Exposure level Effect or symptom |
|_________________________________________________________________ |
| On humans |
|10 ppm Eye irritation |
|20 ppm for more Irritation to the eyes, nose, |
|than 20 min. and throat |
|50 to 100 ppm Vomiting, nausea, diarrhea |
|200 ppm for 1 hr. Dizziness, nervous system |
| depression increased |
| susceptibility to pneumonia |
|500 ppm for 30 min. Nausea, excitement, |
| unconsciousness |
|600 ppm and above Rapid death |
| On swine |
|20 ppm, exposed Fear of light, loss |
|continually of appetite, nervousness |
|200 ppm Possible pulmonary edema |
| (water in the lungs) with |
| breathing difficulties and |
| possible loss of consciousness |
| and death |
|__________________________________________________________________|
____________________________________________________________________
| |
|Table 2. Effects of ammonia gas exposure on humans and swine. |
| |
|_________________________________________________________________ |
|Exposure level Effect or symptom |
|_________________________________________________________________ |
| On humans |
|6 to 20 ppm Eye irritant, respiratory problems |
|and above |
|100 ppm for 1 hr. Irritation to mucous surfaces |
|400 ppm for 1 hr. Irritation to eyes, nose, and throat |
|700 ppm Immediate irritation to eyes, nose, |
| and throat |
|5,000 ppm Respiratory spasms, rapid suffocation |
|10,000 ppm Death |
|and above |
| On swine |
|50 ppm Reductions in performance and health. |
| Long-term exposure increases the |
| possibility of pneumonia |
| and other respiratory diseases. |
|100 ppm Sneezing, salivation, and loss |
| of appetite thereby |
| reducing animal performance. |
|300 ppm and above Immediate irritation of nose and |
| mouth. Prolonged exposure |
| causes extremely shallow and |
| irregular breathing followed by |
| convulsions. |
|__________________________________________________________________|
____________________________________________________________________
| |
|Table 3. Effects of excessive carbon dioxide exposure on humans |
|and swine. |
| |
|_________________________________________________________________ |
|Exposure level Effect or symptom |
|_________________________________________________________________ |
| On humans |
|60,000 ppm for 30 Heavy breathing, drowsiness, |
|minutes and headaches |
|100,000 ppm (10%) Narcotic effect, dizziness, |
|and above unconsciousness |
|250,000 ppm (25%) Death |
|and above |
| On swine |
|40,000 ppm Increased rate of breathing |
|90,000 ppm Discomfort |
|200,000 ppm (20%) Cannot be tolerated by market |
| hogs for more than one hour |
|__________________________________________________________________|
Dust and Particulate Matter
High levels of dust particles resulting from automated dry-
feed handling systems, dander and hair from animals, and dried
manure particles from animals on slotted and solid floors can
occur inside swine units. Manure gases can cling to these dust
particles in such a way that inhaling these gas-laden particles
is like taking a breath of smog. Particulate matter also includes
viral, bacterial, and fungal agents from the building environment
and carries them into a person's respiratory system.
Another potential problem is inhalation of animal feed dust
containing antibiotics. These inhaled particles could cause a
person to become sensitive to certain antibiotics. It is possible
for some workers to contract infections that are resistant to
antibiotics. When a person breathes dusty air for an extended
time there may be several consequences:
o Chronic bronchitis (frequent cough bringing up phlegm) may
result.
o The respiratory system's capacity to take in and exhale oxy-
gen may be reduced.
o There may be an increased susceptibility to respiratory
diseases such as colds and pneumonia.
o Episodes of flu-like illness with fever might develop.
o Adverse allergic reactions may result.
Although NIOSH standards allow for dust exposure to 2.5
mg/m3 desirable and 10 mg/m3 total exposure, excess human and
animal health problems are seen in buildings having greater than
2.5 mg/m3. Dust levels in some swine housing units during the
winter have been reported to be two to three times higher than
the recommended working levels.
Potentially Hazardous Situations
Ventilation breakdown. A ventilation malfunction can result
in severe animal stress or death, particularly on hot, still days
when no natural drafts occur to replace the air in animal areas.
Animals may die from heat prostration, lack of oxygen, or a com-
bination of these hazards.
Manure agitation. When liquid manure that has been stored
for a prolonged period is agitated, toxic levels of hydrogen sul-
fide gas will be released. This situation can create lethal con-
ditions, even when there is full ventilation. The greatest
hazard exists almost immediately after vigorous agitation of
stored manure begins. When this occurs, high concentrations of
gases are released near the building's exhaust fans as well as at
the area around the point of agitation.
Entering a manure storage. A manure storage pit should never
be entered without full respiratory protection. Even if it has
been ventilated or recently emptied, a person could be killed by
hydrogen sulfide gas or by the lack of oxygen. Moreover, the
methane gas that accumulates in the upper stagnant-air areas of
enclosed tanks can create an explosive condition
___________________________________________________________________
|Table 4. Effects of methane exposure or presence on humans and |
|swine. |
| |
|________________________________________________________________ |
|Exposure level Effect or symptom |
|________________________________________________________________ |
|50,000 to 150,000 ppm Potentially explosive |
|500,000 ppm Asphyxiation |
|_________________________________________________________________|
Open manure storage pits, tanks, or lagoons. When an opening
into a deep manure storage pit or tank is unguarded, it invites
an accident. Workers and animals could fall into the pit and
drown. Surface scums and crusts can be deceiving since they may
appear capable of supporting a person's weight, especially a
child's, when in fact, they cannot..
Heaters and engines. Unless there is adequate ventilation
where unit heaters, catalytic heaters, and radiant heaters are
used, carbon monoxide can reach deadly concentrations. Another
hazard is the use of auxiliary generators that are not vented to
the outside.
How to Control Toxic and
Asphyxiating Gases
Insure adequate ventilation. Adequate ventilation systems
should be designed to provide the recommended air exchange rates
within animal and worker zones. When conserving heat during the
winter, be sure to not reduce ventilation rates below the minimum
recommended. Consider using air circulation fans or distribution
ducts to improve the mix of indoor air during the winter.
In addition to maintaining adequate ventilation, observe
these management tips:
o Maintain the ventilation systems by frequently removing dust
accumulations from exhaust fans, fan shutters, and air inlet
screens.
o Place ducts to be used for underfloor exhaust fans below the
slats and above the highest level the manure will reach. Use
them to exhaust air outside.
o Provide the maximum amount of mechanical ventilation possi-
ble whenever stored manure is agitated. In a naturally ven-
tilated building, agitate only when there is a brisk breeze;
and even then, consider removing livestock from the building
before agitating the manure.
o Install an alarm system to warn of power failures that would
affect the mechanical ventilation system. Check and maintain
the alarm system and power unit on a weekly basis. If power
fails, an emergency power generating unit should start
immediately. If an auxiliary unit is not available, open all
windows and doors and consider removing livestock from the
building where manure is stored.
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| |
|Table 5. Effect of carbon monoxide exposure on humans and swine. |
| |
|________________________________________________________________ |
|Exposure level Effect or symptom |
|________________________________________________________________ |
| On humans |
|50 ppm for 8 hr. Fatigue, headaches |
|500 ppm for 3 hr. Chronic headaches, nausea, |
| and impaired mental ability |
|1,000 ppm for 1 hr. Convulsions; coma after |
| prolonged exposure |
|4,000 ppm and over Death |
| On swine |
|200-250 ppm Baby pigs are less vigorous |
|150 ppm and over Causes abortions in late-term |
| sows, and an increased incidence |
| of stillborn pigs. Reduces growth rate |
| of young pigs. |
| |
|_________________________________________________________________|
o Use proper manure storage management. Do not overfill under-
floor manure storage pits. These pits should be pumped or
drained when the liquid level rises to within 1 foot of the
slats or to within 4 inches of the bottom of slat support
beams. Clean the manure pits regularly. After emptying the
pit, add enough liquid to cover the remaining residue and
manure solids. Hydrated agricultural lime can be added to
manure storage contents at the rate of 1 pound per 1,000
cubic feet of stored manure to maintain the pH near 7. Alka-
line conditions suppress the release of hydrogen sulfide but
increase ammonia emissions.
o Placement of gas traps in drain lines connecting outside
manure storage structures with enclosed buildings is recom-
mended.
o Unvented heaters should never be installed unless continuous
ventilation is provided; in other words, vent all engine and
heater exhausts to the outside to minimize carbon monoxide
levels.
Precautionary Measures
o If possible, evacuate all animals and workers from buildings
before stored manure is agitated. If animal evacuation is
not possible, observe from a distance, start agitation
slowly and be ready to turn off the pump at the first sign
of trouble or discomfort. See Tables 1-5 for effects of
exposure to gases. Do not agitate vigorously at the start.
Instead, begin agitating at near tractor idle speed and
slowly build up the pump speed.
o Never look into a manure storage when agitating. Never try
to rescue a distressed animal or person without being
equipped with self-contained breathing apparatus that has
its own oxygen supply.
o Enter a manure storage pit or tank only when it is abso-
lutely necessary. Even then, only do so if it is well-
ventilated and if you are wearing a self-contained breathing
apparatus with a lifeline attached. Make certain a simi-
larly equipped person who is capable of retrieval is ready
and strategically located for rescue.
o Be aware of the signs which indicate gas has reached toxic
levels. These signs include rapid blackening of copper
pipes, electrical wiring, or lead-pigmented paintor white
deposits of zinc sulfate on galvanized steel. Approved com-
mercial gas monitors, measuring devices, or kits can be used
to check gas levels.
o To help prevent the risk of drowning, construct covers for
ground-level and below-ground manure collection and storage
tanks. Once installed, keep these access covers in place.
Covers should be round or chained to the floor to prevent
them from falling into the pit. Install railings around all
manure storage pit or tank openings, walkways alongside the
structures, and piers or catwalks over the open storage
areas. Attach permanent ladders made of noncorrosive
material to the inside wall of all deep manure storage
structures.
Other Safety Precautions
o Fence in earthen manure storage basins and lagoons to keep
out animals and people. Remind people, by posting warning
signs, to exercise utmost caution.
o Prohibit smoking, welding, or the use of open flames in
poorly ventilated buildings or enclosed manure storage areas
until the areas have been thoroughly ventilated.
o Use explosion-proof electric motors. Keep light fixtures and
electric wiring around storage structures in good condition.
All electrical wiring should meet the National Electric
Code.
o Place flame arrestors on the gas lines that lead to heating
units or generator engines.
o The area around the anaerobic digester systems for methan
production should have ``Caution-Flammable'' signs posted in
plain view.
o Keep all guards and safety shields in place on equipment
such as pumps, manure spreaders, and power units.
o Stand clear of ``tipping bucket'' flush tanks when they
rotate.
o When working in enclosed buildings for a prolonged period,
reduce inhalation of dusty air by wearing a disposable dust
mask which has been approved by the American National Stan-
dard Practices for Respiratory Protection, or NIOSH.
First-Aid Procedures
o Be able to recognize symptoms of gas poisoning and the phy-
sical effects that occur as a result of exposure to manure
decomposition and/or heating units.
o Rescue equipment and first-aid supplies that meet the
approved standards of a consulting physician should be
located near the manure storage area.
o Post the phone number of the local fire department or rescue
squad near rescue equipment and beside all telephones.
o Do not attempt to rescue a victim from a storage pit unless
you are equipped with a self-contained breathing apparatus.
o When phoning for emergency medical help, make sure rescuers
know what the situation involves so they can determine the
need for special equipment.
o If the victim can be safely moved, get him or her to fresh
air.
o If the gases have simply irritated a part of the body, flush
the affected areas with fresh water.
o If the victim is not breathing, start cardiopulmonary resus-
citation (CPR, if properly trained) immediately and continue
until medical help arrives.
NEW 1/86 (5M)
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Cooperative Extension Work in Agriculture and Home Economics,
State of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
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.