HOUSING                                           PIH-104


                 Safety in Swine Production Systems

James Barker, North Carolina State University
Stanley Curtis, University of Illinois
Ordie Hogsett, University of Illinois
Frank Humenik, North Carolina State University

Kelley Donham, University of Iowa
Ken Kreig, University of Alaska
John Sweeten, Texas A&M University


     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

     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

     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

     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.

|                                                                  |
|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

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

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.
|                                                                 |
|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-

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

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

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

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

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

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)


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,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service  of  Purdue
University  that  all  persons  shall  have equal opportunity and
             access to our programs and facilities.