Carbon Monoxide 

Carbon monoxide (CO) is a colorless, odorless gas that can be generated both on the farm and in the home. At high concentrations, CO can cause asphyxiation or stop your brain from getting good oxygen exchange with your blood. Understanding the signs and symptoms of exposure and where it is generated are both important to preventing death in the community. In the United States, around 430 people die from accidental carbon monoxide poisoning, and 50,000 people visit the emergency room every year because of exposure to carbon monoxide.

Signs and Symptoms

Exposure Routes: Inhalation, skin and/or eye contact

Low Concentrations (<9 ppm): Comfortable living concentration.

• • NIOSH REL-TWA: 35 ppm (8-hour allowable)
  • OSHA PEL-TWA: 50 ppm

Medium Concentrations (200 ppm): Headache, dizziness, nausea in 2 hours.

High Concentrations (400 ppm): Life threatening in 3 hours.

• • IDLH: 1200 ppm

Sources

Any combustion process has the possibility of creating Carbon Monoxide. Using gas or diesel engines indoors can create an environment that is considered an oxygen deficient atmosphere.

• • Gas-Fired Heaters (combustion byproducts)
  • Inside Grain Bins (out-of-condition grain; gas-fired dryers)
  • Grain Bin Equipment (overheated equipment; smoldering product)

Activity: Using gas or diesel engine indoors (power-washing, skid loader, etc.)

Respiratory Protection

NOTE: No air purifying respirator is effective. Ventilate the area and use:

Self-Contained Breathing Apparatus (SCBA)

Resources for Carbon Monoxide

• • Carbon Monoxide in Grain Storage Structures [Poster] – Confined Space Safety: Grain Storage Structure Entry Procedures
  • Carbon Monoxide in Manure Storage [Poster] – Confined Space Safety: Steps for Entry into Manure Storage

Carbon Dioxide 

Carbon dioxide (CO2) is a colorless, odorless gas produced by the respiration of plants and animals, as well as from open-flame, non-vented space heaters. It is denser than air and can accumulate in areas such as animal pens, manure tanks, and silos, posing a risk of oxygen deficiency which can lead to asphyxiation. While well-ventilated livestock buildings typically do not have harmful CO2 levels, dangerous concentrations may occur in sealed silos, liquid manure storages, and grain storages.

High levels of carbon dioxide can cause drowsiness, dizziness, and trouble concentrating. As concentrations increase, it could cause elevated heart rate, elevated blood pressure, asphyxia, and convulsions at extremely high concentrations.

Signs and Symptoms

Exposure Routes: Inhalation, skin and/or eye contact

Low Concentrations (600-1000 ppm): Muscle stiffness

Medium Concentrations (1000-2500 ppm): Labored breathing, drowsiness and headache.

• • NIOSH REL: 5000 ppm (8-hour maximum)

High Concentrations (30,000 ppm or 3%): Increased pulse rate, nausea, impairment. Can displace enough oxygen to cause death by suffocation.

Sources

Carbon dioxide gas is heavier than air – it can settle near the bottom of the manure pit.

• • Gas-Fired Heaters (combustion byproducts)
  • Animals (exhaled breath)
  • Inside Grain Bins (out-of-condition grain; gas-fired dryers)
  • Grain Bin Equipment (overheated equipment; smoldering product)
  • Silos (naturally fermenting silage)
  • Product of decomposition

Activity:

Control Measures: 

Respiratory Protection 

Resources for Carbon Dioxide

Nitrogen Dioxide 

Nitrogen dioxide (NO2) is a hazardous asphyxiant produced as a result of chemical reactions that take place almost immediately after plant material is placed into a silo, posing a risk of sudden death even with short-term exposure. It has a bleach-like odor and appears as a reddish-brown haze, being denser than air and often accumulating above the silage surface. Weather conditions and agricultural practices influence nitrate levels in plants, leading to NO2 production in silos. For instance, a dry growing season followed by heavy rainfall can cause corn to absorb high nitrate levels, which, if harvested prematurely, leads to the generation of NO2 through chemical reactions.

Signs and Symptoms

Medium Concentrations (1-4 ppm): Changes in respiratory function and pulmonary pathology.

High Concentrations (50 ppm): Progressive respiratory injury; possible death.

Sources

• • Silos (naturally fermenting silage)

Activity: Entry into a non-air tight silo

Control Measures:

Respiratory Protection

NOTE: Do not enter for at least 10-14 days after filling without running blowers for at least 30 minutes, monitoring nitrogen oxide levels to assure nontoxic levels and wearing SCBA if elevated levels are present.

Self-Contained Breathing Apparatus (SCBA)

Resources for Nitrogen Dioxide

Hydrogen Sulfide 

Hydrogen sulphide (H2S) is the most dangerous of the manure gases. It is classified as a chemical asphyxiant because it immediately chemically interacts with the blood’s hemoglobin to prevent oxygen from being carried to the body’s vital organs and tissues. It is produced from the anaerobic decomposition of organic materials such as manure. Its characteristic rotten egg smell is easy to detect at low concentrations, but at higher concentrations, H2S paralyzes the sense of smell. 

Signs and Symptoms

Hydrogen sulfide attacks the eyes and is a severe eye irritant that may cause tissue damage.

Low Concentrations (2-20 ppm): Dizziness, headache, nausea and irritation of respiratory tract.

High Concentrations (500-700 ppm): Unconsciousness, respiratory failure and death within minutes.

NOTE: Hydrogen sulfide may be explosive at a wide range of concentrations in air – 4.3% – 46% by volume.

Sources

Hydrogen sulfide gas is heavier than air – it can settle near the bottom of the manure pit.

• • Manure Storage (under slatted floor; outside lagoon, pit or tank)
  • Manure Pumping (under slatted floor; outside lagoon, pit or tank)
  • Manure Agitation
  • Foaming Manure

Activity: Livestock and Poultry Confined Animal Feeding Operation (CAFO)

Respiratory Protection

NOTE: Restrict entry, ventilate area

Supplied Air Respirator

*Also referred to as “Airline Respirator”

Self-Contained Breathing Apparatus (SCBA

Resources for Hydrogen Sulfide

• • GPCAH Manure Gas Topic Page [Webpage]: Manure Gas Safety
  • Hydrogen Sulfide in Grain Storage Structures [Poster] – Confined Space Safety: Grain Storage Structure Entry Procedures
  • Hydrogen Sulfide in Manure Storage [Poster] – Confined Space Safety: Steps for Entry into Manure Storage
  • Response to Hydrogen Sulfide Concentrations [Poster]: Gas Monitor Use

Ammonia

Ammonia (NH3) is a colorless gas with a strong odor, produced by the decomposition of nitrogen compounds in animal manures. It is classified as an irritant and may cause respiratory diseases in livestock if exposed to high levels for long periods. Eye irritation occurs at 20–50 ppm, varying by sensitivity. Ammonia is primarily a concern in swine and poultry facilities, as well as in manure composting. Improving ventilation is advised if eye irritation is observed in livestock or humans.

Signs and Symptoms

Exposure Routes: Inhalation, ingestion, skin or eye contact

Low Concentrations (5-20 ppm): Odor, eye irritation

Medium Concentrations (20-50 ppm): Moderate irritation of the eyes, nose and throat; breathing difficulty, wheezing, chest pain.

• • NIOSH PEL: 30 ppm
  • OSHA PEL: 50 ppm

High Concentrations (2500 ppm): Chemical pneumonitis, pulmonary edema, pink frothy sputum, cyanosis; skin burns, vesiculation; death. Liquid Ammonia: frostbite.

• • IDLH: 300 ppm

Sources

Ammonia gas is lighter than air.

• • Manure Storage (under slatted floor; outside lagoon, pit or tank)
  • Manure Pumping (under slatted floor; outside lagoon, pit or tank)
  • Foaming Manure
  • Anhydrous Ammonia

Activities: Livestock and Poultry Confined Animal Feeding Operation (CAFO); Anhydrous Ammonia field application

Control Measures: Ventilation if eye irritation is observed in humans or livestock

Respiratory Protection

N95 Filtering Facepiece Respirator (FFR): If Ammonia concentrations are reasonably low (<10 ppm).

• • Examples of Use: Inside animal housing

Half-Mask Respirator with Filtration: Needed if both Ammonia and dust are present and need to be controlled for.

*Also referred to as “Half-Mask Face Piece”, “Cartridge Respirator”

• • Ammonia Gas Cartridge/Canister (Green)
  • Filtration: N or P prefilter (P100 Filter)
  • Examples of Use: Inside animal housing; Anhydrous Ammonia field application (must protect skin and eyes if using half face piece)

Full Facepiece Respirator: Wear if Ammonia concentrations are high (>50 ppm).

• • Ammonia Gas Cartridge/Canister (Green)
  • Examples of Use: Anhydrous Ammonia application

Resources for Ammonia

• • Ammonia in Manure Storage [Poster] – Confined Space Safety: Steps for Entry into Manure Storage
  • Preparation, Application, PPE [Poster] – Anhydrous Ammonia: Farmer Safety Check

Methane 

Methane (CH4) is a colorless, odorless, non-toxic, and combustible gas produced from the anaerobic digestion of organic material. When stored correctly, it serves as a fuel for internal combustion engines or can be cleaned for use in the natural gas grid. Being lighter than air, it tends to rise from manure storage. In well-ventilated areas, methane poses little risk, but in covered storage, it can become concentrated and reach explosive levels.

Signs and Symptoms

Exposure Routes: Inhalation, skin and/or eye contact (liquid)

Low Concentrations (1000 ppm or <0.1%): Not harmful

• NIOSH REL: 1000 ppm
• OSHA PEL: 1000 ppm

Medium Concentrations (10,000 ppm or <1%): No known toxicity. 

• IDHL: 2100 ppm (10% LEL)

High Concentrations (50,000 ppm or <5%): Explosive. Dizziness, confusion, excitation, asphyxia. Liquid: Frostbite.

• • IDLH: 300 ppm

Sources

Methane gas is lighter than air – occurs near the top of manure pits. Expect methane to be present in manure pits.

• • Manure Storage (under slatted floor; outside lagoon, pit or tank)
  • Manure Pumping (under slatted floor; outside lagoon, pit or tank)
  • Foaming Manure (if foaming manure is present, significant Methane risk)

Activity: Livestock and Poultry Confined Animal Feeding Operation (CAFO)

Control Measures: Methane is an explosion hazard, make sure to prevent sparks when concentrations are detected and ventilate the area.

Respiratory Protection

NOTE: Ventilate area

Supplied Air Respirator:

*Also referred to as “Airline Respirator”

Self-Contained Breathing Apparatus (SCBA):

Resources for Methane

• • GPCAH Manure Gas Topic Page [Webpage]: Manure Gas Safety
  • Response to Methane Concentrations [Poster]: Gas Monitor Use

Organic Dusts

More information about organic dusts.

Sources

• • Feed or grain dust
  • Mold
  • Spores
  • Animal dander

Activities:

• • Livestock and Poultry Confined Animal Feeding Operation (CAFO)
  • Grain Handling: Silo or bin unloading

Respiratory Protection

Filtering Facepiece Respirator (FFR): 

• • Filtration: N, R, or P series

Half-Mask Respirator with Filtration: Wear with the correct cartridge or canister if hazardous gas or vapors are also present.

*Also referred to as “Half-Mask Face Piece”, “Cartridge Respirator”

• • Filtration: N or P series

Full Facepiece Respirator: Wear with the correct cartridge or canister if hazardous gas or vapors are also present and eye/skin protection is needed.

• • N or P series

Powered Air-Purifying Respirator (PAPR): 

• • Filtration: HEPA Filter

Resources for Organic Dusts

• • Organic Dusts in Grain Storage Structures [Poster] – Confined Space Safety: Grain Storage Structure Entry Procedures