Prevalent Poultry Barn Gases
Gas Characteristic Source TLV*(max Comment



Colourless and odourless

Animal respiration

5,000 ppm

(8-hour day)

Non-toxic, but elevated levels will displace oxygen at floor level



Colourless, odourless, toxic, non-flammable Burning fossilfuel (gasengines

25 ppm

(8-hour day)

Asphyxiant; toxic concentrations quickly absorbed; may cause illnesses in humansand poultry.
Ammonia(NH3) Pungent, recognizable by acrid smell, and colourles Bacteria that live in faeces and urine

25 ppm

(8-hour day

Most prevalent of all barngases – irritates mucous membranes of eyes, nose, and upper respiratory tract; long periods of exposure may cause respiratory diseas.



Highly flammable, colourless, and odourless Manure pits 5% max concentration in air Highly explosive; simple asphyxiant, though rarely reaches danger threshold for oxygen deprivation



Rotten eggs smell at low concentrations; highly toxic, numbs sense of smell at high concentrations; flammable at 4% concentration in air Breakdown of manure in areas where there is no oxygen (silos,  manure pits) 10 ppm at any time 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50). Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath

*TLV = threshold limit value, the airborne concentration of a substance to which an average person can be exposed repeatedly without any adverse effects.

1 Chart extracted from the Emergency Management Guide for BC Pork Producers, 2015. TLVs are based on the American Society of Agricultural and Biological Engineers’ Safety Standard, 2005. Refer also to OMAFRA Factsheet Hazardous Gases on Agricultural Operations