Manure Pit Hazards

Manure Pits Kill Entire Families — Usually When Someone Tries to Help

Manure pits and storage systems are essential infrastructure on many Texas livestock operations, but they're also one of the most dangerous environments on any farm or ranch. The toxic gases from decomposing manure can kill within seconds — and have claimed entire families in single incidents when rescuers rushed in without understanding the invisible threat.

Unlike many farm hazards that give you warning signs, manure pit gases can overwhelm you before you have time to react. Understanding these hazards, respecting the danger, and following strict safety protocols is the only way to work safely around these systems.

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The Deadly Gases of Manure Storage

Decomposing manure produces four main hazardous gases, commonly called the "Manure Gas Quartet":

1. Hydrogen Sulfide (H₂S) - The Silent Killer

• Deadens the sense of smell at dangerous levels (olfactory fatigue)
• Heavier than air—accumulates at the bottom of pits
• Extremely toxic—lethal at concentrations above 700 ppm
• Can cause immediate unconsciousness at high levels

2. Methane (CH₄)

• Odorless and colorless
• Highly explosive (5-15% concentration in air)
• Displaces oxygen, causing suffocation
• Asphyxiation in poorly ventilated areas
• Can migrate through soil into adjacent buildings

3. Carbon Dioxide (CO₂)

• Odorless and colorless
• Displaces oxygen
• Present in all manure storage systems
• 7-10%: Unconsciousness within minutes
• Higher levels: Rapid death from asphyxiation

4. Ammonia (NH₃)

• Lighter than air—rises
• Irritating to eyes and respiratory system
• Generally not lethal except at very high concentrations
• Can cause chemical burns to lungs and eyes

When Gas Concentrations Spike

Manure pit gases are not constant. Concentrations can spike dramatically under certain conditions:

Agitation

• Gases trapped in the liquid get released suddenly
• H₂S concentrations can increase 100-fold in seconds
• A pit that seemed safe becomes lethal instantly

Temperature Changes

• Warm weather increases gas production
• Sudden temperature increases after cool periods release accumulated gases
• Texas summers create particularly hazardous conditions

Disturbance

• Adding fresh manure
• Pressure washing nearby
• Equipment entering storage areas
• Pumping or emptying operations

Storms and Weather

• Barometric pressure changes affect gas release
• Post-storm periods can see gas spikes
• Wind patterns can concentrate gases in unexpected areas

Types of Manure Storage Systems

Below-Ground Pits

• Outdoor below-grade pits
• Basement storage systems

Above-Ground Tanks

• Open-top vs. covered designs
• Often require entry for maintenance

Lagoons and Earthen Basins

• Low areas around lagoons can have lethal gas concentrations
• Wind conditions affect exposure risk dramatically

Covered Storage

• Sudden release when covers are lifted
• May have hatches or entry points that become confined spaces

Fatal Scenario: How Incidents Unfold

A typical manure pit fatality follows a tragic pattern:

• Initial victim enters or approaches pit (often during routine work, agitation, or to retrieve fallen equipment)
• Victim is overcome by H₂S within seconds—often before they can call out or escape
• Second victim sees collapse and rushes to help
• Second victim is overcome attempting rescue
• Third, fourth, or more victims follow the same pattern

Prevention: Safe Work Practices

Around Manure Storage

• Stay upwind whenever possible
• Recognize that low-lying areas may have dangerous gas accumulation
• Never assume a space is safe based on smell
• Know the signs of exposure (see below)

During Agitation

• Evacuate buildings connected to below-floor storage
• Open all possible ventilation
• Make sure workers are positioned upwind
• Have emergency plan in place
• Never enter enclosed areas containing pits
• Position workers for wind escape routes
• Monitor continuously for symptoms
• Be prepared to evacuate immediately

Entry Protocols (When Absolutely Necessary)

Entry into any manure storage area — pits, tanks, pump rooms — must follow strict confined space procedures:

• Question the necessity: Can the work be done without entry?
• Complete lockout/tagout: Disable all agitation equipment, pumps, and connected systems
• Test atmosphere: Use a calibrated 4-gas monitor for:
• Oxygen (19.5-23.5%)
• Hydrogen sulfide (below 10 ppm)
• Methane (below 10% LEL)
• Carbon dioxide (below 5,000 ppm)
• Ventilate: Force fresh air into space for extended period before entry. Continue ventilation throughout work.
• Continuous monitoring: Keep gas detector running during entire entry
• Attendant stationed: Trained person must remain outside at all times
• Rescue equipment ready: Retrieval system, harness, communication
• Never trust ventilation alone: Continue atmospheric monitoring even with mechanical ventilation running

Recognizing Exposure Symptoms

Know the warning signs of manure gas exposure:

Early/Mild Exposure

• Headache
• Dizziness
• Nausea
• Eye irritation
• Coughing
• Fatigue

Moderate Exposure

• Severe headache
• Disorientation/confusion
• Difficulty breathing
• Loss of coordination
• Burning sensation in eyes and throat

Severe Exposure

• Unconsciousness
• Seizures
• Respiratory failure
• Cardiac arrest

Emergency Response

If Someone Collapses Near Manure Storage

• Do NOT rush in to help
• You will likely become a victim
• This is how multiple fatalities occur
• Call 911 immediately
• Report it as a toxic gas/confined space emergency
• Give exact location
• Describe the situation
• Attempt rescue ONLY if safe
• From upwind position
• Without entering the hazardous area
• Using retrieval equipment if available
• With self-contained breathing apparatus (SCBA)
• If victim can be safely reached:
• Move them to fresh air
• Begin CPR if not breathing
• Remove contaminated clothing if safe
• Keep warm and quiet
• Provide information to responders:
• Type of storage system
• Recent activities (agitation, pumping)
• Number of victims
• How long exposed

First Responder Considerations

• Manure pit rescues require specialized equipment
• SCBA is mandatory for entry
• Standard procedures may not address agricultural scenarios
• Local fire departments may need specific training on farm confined space rescue

Building Safety Infrastructure

Physical Safeguards

• Guardrails around open lagoons and pits
• Locked access points
• Make sure natural ventilation paths aren't blocked
• Consider continuous low-level ventilation
• Consider fixed gas detection in high-risk areas
• Alarm systems for buildings with under-floor storage

Equipment

• Personal H₂S monitors for high-exposure work
• Self-contained breathing apparatus for rescue
• Ventilation fans (explosion-proof for enclosed spaces)
• Rescue equipment (tripod, harness, retrieval winch)

Design Considerations for New Systems

When building or upgrading manure storage:

• Above-ground preferred over below-ground
• Outdoor preferred over under-building
• Maximize natural ventilation
• Include safe access points for maintenance
• Design for minimal entry requirements
• Install permanent ventilation systems

Special Considerations for Texas Operations

Heat and Gas Production

• Early morning work around pits (before heat peaks)
• Enhanced ventilation during hot periods
• More frequent atmospheric monitoring

Drought and Concentration

Hurricane and Flood Season

• Lagoons may overflow or mix with floodwater
• Structural integrity may be compromised
• Gas concentrations may be unpredictable

Scale of Operations

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Training Requirements

Everyone who works around manure storage needs:

• Hazard awareness training
• Gas identification and effects
• Risk factors and danger periods
• Warning signs of exposure
• Safe work practices
• Agitation procedures
• Entry protocols
• Emergency response
• Equipment training
• Gas detector operation and calibration
• PPE use and limitations
• Rescue equipment
• Annual refresher training
• Review incidents and near-misses
• Update procedures as needed
• Reinforce key safety messages

Bottom Line

• Manure pit gases can kill in seconds. There's no safe "quick" exposure.
• You can't smell dangerous H₂S. High concentrations paralyze your sense of smell.
• Agitation is the most dangerous time. Gas releases can spike 100-fold during pumping and stirring.
• Never attempt rescue without protection. Most manure pit victims are would-be rescuers.
• Test, ventilate, test again. Atmospheric conditions can change rapidly.
• Never work alone. Always have someone positioned safely outside who can summon help.
• When in doubt, stay out. If conditions aren't verified safe, don't enter.

Resources

• OSHA Agricultural Confined Spaces: osha.gov
• Iowa State University Extension: extension.iastate.edu/ag/manure
• NIOSH Manure Gas Safety: cdc.gov/niosh
• Texas AgriLife Extension: agrilifeextension.tamu.edu
• Poison Control Center: 1-800-222-1222

• Atmospheric Testing
• Ventilation Before Entry
• Rescue Planning for Confined Spaces