Since the increased use of manure pits by Michigan livestock producers, there have been several instances where a farmer, family member, or employee has asphyxiated or succumbed to toxic gases from the pit. Cases have been reported where several individuals have died while attempting to rescue a coworker or family member from a pit.
Nationwide data shows that most deaths occur during the summer months, a time when many producers are emptying pits. Regardless of the season, it is always best to presume that the pit contains hazardous gases or lacks oxygen. Producers need to take protective measures to protect themselves and others working in or around the pit.
The four main gases produced from decomposing manure are hydrogen sulfide, methane, ammonia, and carbon dioxide. In high concentrations, each of these gases may pose a health threat to humans and livestock (see Table 1). In swine housing facilities, where the manure pit is often located below the facility floor, these gases are generally detectable in low concentrations throughout the year. When pits are agitated for pumping, some or all of these gases are rapidly released from the manure a d may reach toxic levels or displace oxygen, increasing the risk to humans and livestock.
|Table 1. Acute Effects of Swine Confinement Air Contaminants on Humans*|
|Gas||Exposure level||Effect or symptom|
|Hydrogen Sulfide||5 ppm||RECOMMENDED MAXIMUM FOR HUMAN HEALTH|
|10 ppm||Eye irritation|
|20 ppm for >20 minutes||Irritation to the eyes, nose and throat|
|50 to 100 ppm||Vomiting, nausea, diarrhea|
|200 ppm||Dizziness, nervous system depression, increased susceptibility to pneumonia, fluid in the lungs with prolonged exposure|
|500 ppm for 30 minutes||Nausea, excitement, unconsciousness|
|600 ppm and above||Rapid death|
|Ammonia||5 ppm||Lowest concentration detectable by smell.|
|7 ppm||RECOMMENDED MAXIMUM FOR HUMAN HEALTH|
|6 - 20 ppm and above||Eye irritation and respiratory problems|
|40 - 200 ppm||Headache, nausea, reduced appetite, irritation to airways, nose and throat|
|Carbon Monoxide||50 ppm||RECOMMENDED MAXIMUM FOR HUMAN HEALTH|
|50 ppm for 8 hours||Fatigue, headaches|
|500 ppm for 3 hours||Chronic headaches, nausea and impaired mental ability|
|1,000 ppm for 1 hour||Convulsions, coma after prolonged exposure|
|4,000 ppm and over||Rapid death|
|Methane||50,000 to 150,000 ppm||Potentially explosive|
|Carbon Dioxide||1,500 ppm||RECOMMENDED MAXIMUM FOR HUMAN HEALTH|
|20,000 ppm||Deep, rapid breathing|
|40,000 to 60,000 ppm||Heavy breathing, drowsiness, for 30 minutes and headaches|
|100,000 ppm and above||Narcotic effect, dizziness, unconsciousness|
|250,000 ppm and above||Death|
|Dust||2.4 mg/cubic meter||RECOMMENDED MAXIMUM FOR HUMAN HEALTH Cough and increased phlegm (bronchitis), fewer episodes, chest tightness.|
|Endotoxin||0.08 micrograms/cubic meter||RECOMMENDED MAXIMUM FOR HUMAN HEALTH Decreased lung efficiency|
|0.1 micrograms/cubic meter||Organic Dust Toxic Syndrome|
|* - Adapted from Baker J., Curtis S., Hogsett, O., et al ; Safety in swine production systems, Pork Industry Handbook, publication PIH-104, Cooperative Extension Service, Purdue University, West Lafayette, Indiana, 1986. Tables 1,2 and 3.|
Concentrations of hydrogen sulfide above 600 ppm can kill an individual after taking only one or two breaths. The person falls immediately, apparently unconscious and dies without moving again. A safe evacuation of the individual can be made only if the rescuer is wearing a self-contained breathing apparatus (SCBA). Generally, a rescuer has about six minutes to begin cardiopulmonary resuscitation (CPR) before brain damage/death occurs. Unless the rescuer is wearing SCBA protective equipment (see section on personal protective equipment), there is a strong likelihood that the rescuer will also succumb to the toxic gases or lack of oxygen. There have been numerous instances where several farmers have been killed while attempting to remove someone from a pit or facility.
At lower concentrations, hydrogen sulfide can cause severe illness and irritate the entire respiratory track and eyes. Symptoms may include nausea, stomach distress, belching, coughing, headache, dizziness, irritation of the eyes and blistering of the lips.
It is a common belief among farmers that it is safe to enter a facility or pit if they cannot smell the putrid, rotten egg odor associated with hydrogen sulfide. This is not necessarily true because high concentrations of hydrogen sulfide paralyzes the nerve cells of the nose to the point where the person can no longer smell the gas.
Hydrogen sulfide, because it is heavier than air, accumulates above the liquid level of the pit. Individuals may be quickly overcome with hydrogen sulfide when working around a pit, whether it be climbing down a ladder to make repairs or when leaning down to take a manure sample.
Concentrations ranging from 6 to 20 ppm and above will irritate the eyes and throat. At higher concentrations, ammonia can irritate the respiratory system and cause wheezing and shortness of breath. Concentrations above 2500 ppm are considered to be dangerous to human life, but individuals are not likely to enter a facility with a concentration this high because of the extremely strong odor.
Although non-toxic to humans and livestock, methane can cause asphyxiation if it displaces the oxygen in a closed facility.
PROTECTION DURING PIT ENTRY
A self-contained breathing apparatus supplies the wearer with 15 to 30 minutes of safe air to breath. A SCBA system, similar to those worn by firefighters, has a small air tank and facemask that allows the person to move about freely in an area where toxic gases or insufficient oxygen is suspected.
There are restrictions to wearing a SCBA that should be considered before purchasing the equipment. Training on the use of a SCBA is essential to ensure proper use. The facemask must fit properly or toxic gases may enter the mask. The wearer cannot have a beard because the facemask will not seal properly around the face. Your local fire department is the best source for information and training on its use. The cost of a SCBA is about $1,700.
Due to the equipment requirements and inherent risks associated with entering an area where there may be toxic gases or insufficient oxygen, you should consider hiring a professional trained in working in these areas to perform maintenance tasks. If hiring a professional or using a SCBA is not possible, the best advice is to stay out of the pit.
Meters and Ventilation An alternative to wearing a SCBA is to check gas and oxygen levels of a facility or manure pit with a gas and oxygen testing meter before entering (see Table 2 for types of meters and gases that they can detect).
|Table 2. Gas Measuring Devices Useful in Confinement Buildings|
|Gas||Situations*||Detector Tubes||Dosimeter Tubes||Solid state Detectors|
|Ammonia||routine measurements||satisfactory||preferred||Not reliable|
|Hydrogen Sulfide||routine measurements||preferred||satisfactory||satisfactory|
|emergency situations||satisfactory||too slow||preferred**|
|Carbon Monoxide||routine measurements||preferred||satisfactory||satisfactory|
|emergency situations||preferred||too slow||preferred|
|Carbon Dioxide||routine measurements||satisfactory||satisfactory||satisfactory|
|emergency situations||preferred||too slow||satisfactory|
|Methane||flammable levels||preferred||not available||satisfactory|
- Routine is defined as typical daily average concentrations.
Emergency is defined as any non-routine situations such
as pit pump-out, ventilation or electrical failure, observation
of abnormal swine behavior, or unusual respiratory symptoms
in persons entering buildings which may indicate gas concentrations
immediately hazardous to human health.
** - Solid state detectors are preferred here because of the speed or response and because they provide continuous information on hydrogen sulfide concentrations.
|Table 3. How to Measure Hydrogen Sulfide*, Carbon Monoxide, and Carbon Dioxide During Emergency Situations**|
- Note that monitoring hydrogen sulfide concentrations
is recommended whenever a deep pit underneath a building
is being pumped, even if there are no indications of toxic
** - Emergency is defined as any non-routine situation such as pit pump-out, ventilation or electrical failure, malfunction of fossil fuel-burning heaters, observation of abnormal swine behavior or death, or unusual respiratory symptoms of persons entering the buildings. These symptoms may indicate gas concentrations immediately hazardous to human health.
The three basic types of meters are detector tube, dosimeter tube and solid state detectors. Detector and dosimeter tubes use inexpensive gas sampling devices that give reliable readings for ammonia, hydrogen sulfide, carbon monoxide, carbon dioxide, or other gases found on the farm. Dosimeters are best for measuring average concentrations; detector tubes do the best job of measuring instantaneous concentrations during emergency situations. Solid state detectors give continuous readings and have audible alarm systems, but are more expensive than tube type detectors and must be calibrated frequently.
Additional Equipment Anyone entering a pit should be equipped with an approved harness and a rescue rope attached to a tripod and pulley system. Two people can remove an unconscious individual from a pit in a few seconds with this type of a emergency lift. Remember, you have only six minutes to begin cardiopulmonary resuscitation (CPR) before brain damage/death occurs.
Unsafe Alternatives The cost of a self-contained breathing apparatus, metering, and approved equipment to lift an unconscious individual from a pit may lead you to consider less costly alternatives. Unfortunately, all these alternatives have substantial safety risks.
Do not Enter any Confined Manure Pits Without Either:
A self-contained air supply like those fire fighters use. (Dust masks or other cartridge respirators will not filter out the toxic gases nor will they provide the oxygen requirement to work in confined spaces such as manure pits.)
Remember, you have only six minutes after a person stops breathing to begin mouth-to-mouth resuscitation before brain damage/death occurs. Being prepared will greatly reduce the risk of panic, ill adverse action, and needless death or injury.
Reducing Hazards from Manure Gases
State University, Agricultural Engineering Department.
Howard J. Doss, Extension Agricultural Safety Specialist; Howard L. Person, Extension Agricultural Engineer; and William McLeod, Agricultural Engineering, Michigan State University Extension, East Lansing, Michigan 48824. 5/93. Funded by the National Institute of Occupational Safety and Health - #UO5/CC-4506052-02.
This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by the MSU Extension or bias against those not mentioned.
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