Monitoring Manure Gases

Use the following format to cite this article:

Monitoring Manure Gases. (2012) Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from


The four main toxic gases found in manure storage areas are ammonia, carbon dioxide, hydrogen sulfide, and methane. Due to the toxicity of these gases, you must check and monitor gas levels in confined space manure storage areas prior to entering them and while in them.

Additionally, you must monitor oxygen levels to ensure that spaces contain adequate supplies of air.

Portable electronic gas monitors are available to test the levels of both toxic gases and oxygen in a confined space, but it is important to ensure that the monitor you choose will test the level of all the relevant gases.

Portable Electronic Gas Monitors

Handheld Gas Monitor

Handheld Gas Monitor

(Source: Pennsylvania State University. Agricultural Safety and Health)

Depending on your budget, you can borrow, lease, or purchase electronic gas detection equipment. There are two types of gas detection devices for monitoring manure storage areas:

  • Installed monitors: Installed, or fixed, gas detection systems are typically more costly and not practical for confined space manure storage areas because such environments corrode a monitor’s electrical components.
  • Portable monitors: These devices are recommended over installed monitors because they can be stored in a protected space when not in use. They include portable electronic single-gas or multigas monitors. 

Methane is explosive at certain concentrations; hydrogen sulfide is lethal at high concentrations; low levels of oxygen can be deadly. A single-gas monitor measures only one of these components. A multigas monitor should have the capability to detect dangerous levels of hydrogen sulfide and methane and dangerously low concentrations of oxygen (0% to 30% by volume). Therefore, a monitor with multigas capabilities provides more information prior to a person entering a potentially dangerous space. 

Gas Monitors with Pumps

Some portable electronic gas monitors are equipped with pumps that allow them to test gas levels without being carried into manure storage areas. During the sampling process, the pump’s plastic tube is lowered into the storage area to within a few inches of the manure surface. The tube should never touch the manure. Measurements should be taken at multiple locations above the manure surface.

Gas levels should be tested at two locations in the confined space for different gases:

  • At the manure surface for the heavier gases carbon dioxide and hydrogen sulfide.
  • In the air approximately 12 inches below the top of the storage unit for the lighter gases ammonia and methane.

Measurements should be done prior to entry and continuously while any person is in the confined space. 

Gas Detection Badges

Another portable device is a gas detection badge, which is worn by a worker to track his or her exposure to contaminants. However, gas detection badges are not recommended for use in confined space manure storage areas because they may give inaccurate readings and they do not provide timely results. In addition, a gas detection badge may not provide readings for oxygen levels.

Gas Detector Tubes

A gas detector tube is a single-use gas detection device that provides a reading for one specific gas. Gas detector tubes do not monitor oxygen levels and provide only an approximate reading for the air being sampled.  

Maintenance of Portable Equipment

Regular maintenance, testing, and calibration of gas monitoring equipment enable it to work properly and extend its life. Maintenance and calibration are generally simple to execute. Follow the manufacturer’s recommendations when calibrating your monitor and use the certified standard gas concentrations. When possible, calibrate your monitor under environmental conditions that are similar to those where you will be using the monitor. As the device ages, calibration often becomes more difficult to complete, and you may need to replace the device or gas sensors. 

Before using a portable electronic gas monitor, remember to fully charge the device or to have fresh batteries available.

Store the device in a clean, dry, dust-free storage container. 


Use the following format to cite this article:


Monitoring Manure Gases. (2012) Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from



Ogejo, J. (2009) Poultry and livestock manure storage: Management and safety. Virginia Cooperative Extension. Retrieved from

Steel, J., Murphy, D., and Manbeck, H. (2011) Confined space manure gas monitoring. Penn State Extension. Retrieved from


Reviewed and Summarized by:
Linda M. Fetzer, Pennsylvania State University –
Davis E. Hill, Pennsylvania State University (Has since retired)
Dennis J. Murphy, Pennsylvania State University (Has since retired)
J. Samuel Steel, Pennsylvania State University (Has since retired)
Aaron M. Yoder, University of Nebraska Medical Center –

Respiratory Illnesses Associated with Agriculture

Sunset and wind mills

Photo provided by the Central States Center for Agricultural Safety and Health (CS-CASH)


Use the following format to cite this article:

Respiratory illnesses associated with agriculture. (2012) Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from


A farmer’s or rancher’s life is not always associated with the great outdoors and fresh air. In production agriculture, farmers and ranchers can be exposed to toxic gases and contaminated particulate matter that can cause short- and long-term health problems. The three main respiratory illnesses associated with production agriculture are:

  • farmer’s lung,
  • silo filler’s disease, and
  • organic dust toxicity syndrome. 

Farmer’s Lung

Farmer’s lung, or farmer’s hypersensitivity pneumonitis (FHP), is a noninfectious allergic disease that affects normal lung function. It results from the inhalation of mold spores from moldy hay, straw, or grain. The mold spores that cause farmer’s lung are microorganisms that grow in baled hay, stored grain, or silage with high moisture content (30%). Exposure to mold spores is greater in late winter and early spring.

Mold spores, which are not always visible, are so tiny that 250,000 spores can fit on the head of a pin. Because the spores are so small, it is easy for a farmer or rancher to breathe in millions of spores in a few minutes. Due to their size, the mold spores easily move into and settle in the lower part of the lungs.

Symptoms usually begin four to six hours after exposure to mold spores and can include increased coughing, coughs that bring up mucus, fever, chills, shortness of breath, discomfort in the lungs, and a tightness and/or pain in the chest. Symptoms may become most severe from 12 to 48 hours after exposure.

Allergic reaction to mold spores can be acute or chronic. An acute attack typically resembles the flu or pneumonia. Chronic reactions can resemble a nagging chest cold. A producer who has been diagnosed with farmer’s lung should avoid additional exposure to mold spores; otherwise, the producer’s condition could worsen and render him or her inactive. In some cases, farmer’s lung can be fatal.

If you think that you may have farmer’s lung, contact your physician and explain your symptoms and occupation. If your physician is not familiar with farmer’s lung, you may need to request a referral to a specialist for testing, diagnosis, and treatment.

To reduce the risk of contracting farmer’s lung, take the following steps:

  • Identify and minimize contaminants in your work environment.
  • Avoid exposure to contaminants and mold spores.
  • Limit the growth of mold spores by using mold inhibitors.
  • Harvest, bale, store, and ensile grains at the recommended moisture level to reduce mold growth.
  • Convert from a manual to a mechanical or automated feeding or feed-handling system to reduce the release of airborne mold spores.
  • Move work outside and avoid dusty work in confined areas whenever possible.
  • Mechanically remove air contaminants through ventilation with fans, exhaust blowers, and so on.
  • Wear appropriate respirators, dust masks, or other personal protective equipment (PPE). Click here to learn more about respiratory PPE.

Silo Filler’s Disease

Silo filler’s disease results from inhaling nitrogen dioxide, a silo gas produced during the silage fermentation process. Although a producer who has been exposed to silo gases may not experience symptoms, damage to the lungs may still have occurred. Fluid can build up in a person’s lungs 12 hours after exposure to nitrogen dioxide. Cough, hemoptysis (coughing up blood from the respiratory tract), dyspnea (shortness of breath), and chest pain can occur after an exposure to 20 ppm, a moderate level of nitrogen dioxide. This concentration has been designated by the National Institute for Occupational Safety and Health (NIOSH) as immediately dangerous to life and health (IDLH). Exposure to higher concentrations (greater than 100 ppm) can result in pulmonary edema (fluid accumulation in the lungs) and in swelling in the lungs, leading to long-term respiratory problems or death. Lower concentrations of 15 to 20 ppm are considered dangerous and can cause respiratory impairment.

If you have been exposed to silo gases, even a small amount, seek immediate medical attention.

To reduce exposure to nitrogen dioxide in silo gases, refrain from entering a silo for ten days to three weeks after filling is complete. If entry is necessary after the three-week period, run the silo blower for a minimum of 30 minutes prior to and during entry, and use a portable gas monitor to continually monitor the gas and oxygen levels in the silo. Click here to learn more about silo gases and how to reduce the risk of exposure.

Organic Dust Toxicity Syndrome

Organic Dust Toxicity Syndrome (ODTS), also called grain fever, toxic alveolitis, or pulmonary mycotoxicosis, is caused by exposure to very large amounts of organic dust. Certain agricultural areas may have large amounts of organic dust: grain storage, hog barns, poultry barns, and cotton-processing areas.

The onset of ODTS can occur four to six hours after exposure, and symptoms can be similar to those of acute farmer’s lung and may include cough, fever, chills, fatigue, muscle pain, and loss of appetite. People who have experienced ODTS and who experience additional exposures to organic dust have an increased risk for respiratory problems and the potential for developing chronic bronchitis. Producers can become very sick from ODTS, but most people completely recover. Occurrences of ODTS are underreported because symptoms often resemble the flu or other mild illnesses.  

You can reduce your risk of contracting ODTS by using a respirator to decrease exposure to organic dust. Click here to learn about the different types of respirators used in production agriculture. Implement best management practices to maintain good air quality in confinement buildings for swine and poultry.


Use the following format to cite this article:


Respiratory illnesses associated with agriculture. (2012) Farm and Ranch eXtension in Safety and Health (FReSH) Community of Practice. Retrieved from



Atia, A. (2004) Agri-Facts: Silo gas (NO2) safety. Alberta Agriculture, Food, and Rural Development. Retrieved from$department/deptdocs.nsf/all/agdex9036/$file/726-1.pdf?OpenElement.

Cyr, D. and Johnson, S. (2002) Upright silo safety. University of Maine Extension. Retrieved from

Farmer’s lung. (2008) Canadian Centre for Occupational Health and Safety. Retrieved from

Grisso, R., Gay, S., Hetzel, G., and Stone, B. (2009) Farmer’s lung: Causes and symptoms of mold- and dust-induced respiratory illness. Virginia Cooperative Extension. Retrieved from                                             

Kirkhorn, S. and Garry V. (2000) Agricultural lung diseases. Environmental Health Perspectives. Retrieved from

Murphy, D. (2013) Farm respiratory hazards. Pennsylvania State University Cooperative Extension. Retrieved from

Von Essen, S., Andersen, C., and Smith, L. Organic dust toxic syndrome: A noninfectious febrile illness after exposure to the hog barn environment. Journal of Swine Herd Health and Production. 2005; 13(5): 273-276. Retrieved from


Reviewed and summarized by:
Linda M. Fetzer, Pennsylvania State University –
Karen Funkenbusch, University of Missouri
Dennis J. Murphy, Pennsylvania State University (Has since retired)
Robin Tutor-Marcom, North Carolina Agromedicine Institute
Aaron M. Yoder, University of Nebraska Medical Center –