Liquid-manure-handling systems can reduce labor requirements in confinement facilities but can introduce hazards due to the toxic effects of manure gases, manure runoff into streams, and offensive odors. Outdoor and open-top manure storages can also be potential drowning sites. Under certain conditions, manure gases may be fatal to both humans and livestock. Poor ventilation or ventilation failure in a tightly constructed building can threaten the health and life of animals. To protect humans, manure storage areas should first be ventilated or, where necessary, self-contained breathing equipment should be used when entering manure storage areas. Increased gas levels above manure pits in buildings can also slow the daily gain of animals.
Dangerous situations resulting from manure gases are associated with four main gases that are produced as manure decomposes. These are listed in Table 19 along with some of their characteristics. All of the gases listed in Table 19 are colorless.
Ammonia (NH3) is released from fresh manure/urine and during decomposition. Ammonia levels tend to be high in buildings with litter, solid floors, or scrapers because manure spread over the floor increases ammonia release. Heated floors also increase ammonia release. Ammonia is very soluble in water, so liquid-manure systems release less ammonia. High pH levels cause more ammonia to be released into the air.
Concentrations in ventilated hog buildings have been measured as high as 35 ppm (slightly irritating to eyes and nose) and in unventilated buildings at 176 ppm, which produces extreme discomfort. At 100 to 200 ppm, ammonia causes sneezing, salivation, and loss of appetite for hogs. Prolonged exposure may lead to respiratory diseases in people and animals.
Carbon dioxide (CO2) is released through livestock respiration and manure decomposition, and by unvented heaters. Most of the gas in bubbles coming from stored manure or lagoons is CO2. Death of animals in closed confinement buildings following a ventilation-equipment failure (such as that caused by a power failure) is due in part to excessive CO2. Vigorous agitation of stored manure can release a “slug” of CO2.
Hydrogen sulfide (H2S) is the most toxic gas from liquid manure storage. Dangerous concentrations can be released by agitation of stored liquid manure. Concentrations reaching 200 to 300 ppm have been reported in a building a few minutes after starting to pump out a storage pit and have been as high as 800 ppm during vigorous agitation. Exposure to 200 ppm for 60 minutes will cause headaches and dizziness; 500 ppm for 30 minutes will cause severe headache, nausea, excitement, or insomnia. High concentrations of 800 to 1,000 ppm cause immediate unconsciousness and death through respiratory paralysis unless the victim is moved to fresh air, and artificial respiration is immediately applied. Even the characteristic rotten-egg smell of H2S does not give adequate warning because the sense of smell is rapidly fatigued by H2S, and high concentrations do not give proportionately higher odor intensity.
Methane (CH4) is generated in the decomposition of manure under strict anaerobic (no air) conditions. It is insoluble in water and lighter than air and will accumulate in stagnant air corners in the top of enclosed pits or rooms. CH4 is not toxic, but high concentrations can produce an asphyxiating atmosphere. Concentration in confinement housing is normally well below the lower end of the 5% to 15% explosive range (Table 19). Explosions attributed to methane have occurred around manure storage pits.
| Table 19. Characteristics and Effects of Gases Produced in Decomposing Manure. | ||||
| Gas | Odor | Density | Exposure Limits | Effects |
|---|---|---|---|---|
| Ammonia (NH3) | Pungent | Lighter than air | 10 ppm | Irritation to eyes and nose. Asphyxiating at high levels. |
| Carbon Dioxide (CO2) | None | Heavier than air | 5,000 ppm | Drowsiness, headache. Can be asphyxiating. |
| Hydrogen Sulfide (H2S) | Rotten-egg smell | Heavier than air | 10 ppm | Toxic: Causes headache, dizziness, nausea, unconsciousness, death. |
| Methane (CH4) | None | Lighter than air | 1,000 ppm | Headache, asphyxiant, explosive in 5% to 15% mixture of methane with air. |
| Source: Ohio State University Extension Bulletin 604, 1992 Edition. |
Fatalities may occur when people enter manure-storage structures, including covered manure pits, and are probably due to CO2 and H2S because these gases are heavier than air. Caution should also be taken when agitating manure as the asphyxiating effect of NH3, CO2, and CH4 combined with the toxic effect of H2S could be fatal.
Another potential risk, especially for children, is drowning in a pit, storage tank, and earthen storage basin or lagoon. Failure and breakage of slats or covers on pits and lack of protective barriers or railings around pit openings during agitation can lead to accidents. Push-off platforms or ramps (piers) can be a site for the tractor scraper and driver to tumble into an open storage structure or lagoon. Crusts on earthen storage basins can be a problem, especially for children, as they may appear capable of supporting one’s weight, but they are not.
When designing manure structures and systems, think safety. When operating or managing manure equipment, think safety. Consider the following major safety points when designing and operating manure equipment, structures, or systems:
Take time now to review your total manure management system from a safety viewpoint. Think through each step of the collection system, storage or treatment units, and the land application phase. Are there dangerous areas in construction or operation? If so, make them safe. It could save your life or the life of a loved one or employee.
Every livestock farm should have an Emergency Action Plan in place. What is an Emergency Action Plan and why have one? It is a well-thought-out, simple, basic, common-sense plan that will help those involved with an emergency to make the right decisions. A plan is needed:
Locate first-aid or rescue equipment near the manure-storage area. Clearly mark a wall closet or box and store the equipment inside it. Make occasional checks to ensure the equipment is in good order and has not been removed. Post the phone number of the local fire department/rescue squad on the wall beside the box and also near the telephone.
Personal protective equipment that includes air packs and face masks, nylon lines with snap buckles, and a parachute-type body harness with “D” rings for attaching lines can be obtained from supply sources of industrial safety and hygiene equipment. Look in the yellow pages under safety, safety equipment, industrial safety and hygiene, or safety supplies. These supply sources can also provide information on monitoring or measuring devices used to test hazardous atmospheres. Be sure to specify the gases you are dealing with when asking for or purchasing equipment.
Familiarize yourself, your workers, and your family with the proper operation of all safety equipment. Local medical (rescue) teams can assist in this education.
If members of your family have not taken CPR and first-aid training, enroll them in a course at your earliest opportunity. Periodic refresher courses in CPR are recommended.