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Hydrogen Sulfide Risks in Manure Handling

Hydrogen sulfide is a gas that can be released from stored manure, and it can overcome a person in moments. This guide explains the hazard in general terms and points you to the official sources.

What is hydrogen sulfide and where does it come from?

Hydrogen sulfide is a gas produced when organic material, including livestock manure, breaks down without much oxygen. It is made in pits, tanks, lagoons and under-barn storage, and it can stay dissolved in the liquid until something disturbs it.

Many people know the smell of rotten eggs, but smell is not a safe warning. The gas can dull the sense of smell, so a worker may stop noticing it while the danger is increasing. Never treat the absence of a smell as proof that the air is fine.

When is the risk highest?

Releases are most often tied to disturbing the manure. Agitating a pit, pumping it out, pulling a plug, or moving slurry can send gas into a barn or into the air around the storage in a short time. The hazard is greatest in enclosed or partly enclosed buildings where the gas can collect.

Weather, building layout, how long manure has been stored and what the animals eat all play a part, so no two farms are the same. This is why a written plan for your own site matters more than a rule of thumb from someone else's operation.

• Agitating or pumping a pit
• Removing covers or slats over storage
• Working in a low area near a pit
• Calm, still days when gas does not disperse

Who is most at risk?

Anyone near a pit during agitation can be affected, including family members, hired help, visitors, children and animals. Many tragedies involve a second person who rushed in to help the first, which is why prevention has to include a rule that nobody enters a pit or low confined area to rescue another person.

Livestock deaths in a building are often the first sign of a problem. If animals are in distress during agitation, treat it as an emergency for people too.

How do I prevent exposure during agitation and pumping?

Prevention starts with planning the job before the first pump is turned on. Decide who will be on site, where everyone else will be, how buildings will be ventilated, and how people will leave the area if something changes. Keep children and visitors away from the work area entirely.

Your manufacturer's manuals and your extension agent can describe the correct ventilation approach and the equipment that suits your system. Specific ventilation rates, gas limits and meter settings should come only from an official source, not from this page.

• Plan the job and tell everyone on site
• Keep people and animals out of buildings during agitation as advised by official guidance
• Never work alone near a manure pit
• Follow the equipment manual for every pump and agitator

Do gas monitors help?

A properly chosen, maintained and calibrated gas monitor is one tool in a safety plan. It does not replace ventilation, planning, training or a rule against entry. Monitors need regular checks and replacement of sensors, and the people using them need to understand what the alarms mean and what to do next.

Ask OSHA, NIOSH or your extension office about what kind of monitoring suits manure work, and ask whoever sells or services a device to show you the manufacturer's instructions for it. This site does not recommend specific products.

What should I do if someone collapses near a pit?

Call 911 right away and give the exact location, including the farm address and how to reach the storage. Do not enter the pit, tank or building to reach the person. The air that harmed them can harm you within moments.

Emergency responders have the equipment and training for this kind of call. Your most useful job is to call, stay out of danger, keep others away and be ready to guide responders in. First aid and rescue steps should be learned in a hands-on course, not from an article.

Where can I learn more and get trained?

OSHA and NIOSH publish agriculture-specific guidance on confined spaces and manure gases, and land-grant extension programs run farm safety days and trainings. The University of Iowa and Utah State publications listed below are examples of extension-level resources on manure pit hazards.

Consider asking your local fire department to visit your operation and talk through your site. Many departments welcome the chance to see a farm before an emergency happens.

Last reviewed: November 12, 2026. Written by the Farm Safety Editorial Team. See our editorial policy.