Ammonia · Canairy

What it is

Ammonia (chemical formula NH3) is a colorless gas with a sharp pungent smell that most people detect at around 5 parts per million (ppm) and find clearly irritating above about 25 ppm. It is highly soluble in water (the household cleaner sold as "ammonia" is a dilute solution of NH3 in water). Anhydrous ammonia (the pure liquefied gas) is used widely in agriculture and refrigeration.

Ammonia is a primary precursor to ammonium nitrate and ammonium sulfate particles, which are major components of secondary PM2.5 in many regions, so ammonia indirectly drives a lot of fine particle pollution downwind of farms and feedlots.

Where it comes from

Outdoor ammonia in the U.S. comes mostly from agriculture:

Livestock waste at concentrated animal feeding operations (CAFOs), especially dairies, hog farms, and poultry operations
Fertilizer application (anhydrous ammonia, urea, ammonium nitrate)
Manure storage and land application

Other sources include vehicle exhaust (especially gasoline cars with three-way catalysts, which form some ammonia), wastewater treatment, industrial chemical manufacturing, and ammonia refrigeration systems used in cold storage, ice rinks, and food processing.

Indoor sources include cleaning products (window cleaners, floor cleaners, some degreasers), cat litter boxes, urine, smoke, and certain cosmetics like hair dyes. Mixing ammonia-based cleaners with bleach produces chloramine gas, a separate respiratory hazard, and should always be avoided.

Health effects

Low-level ammonia is irritating but not seriously toxic. Effects scale steeply with concentration:

5 to 50 ppm: odor noticeable, mild irritation in sensitive people
100 to 200 ppm: clear irritation of eyes, nose, throat
400 to 700 ppm: severe irritation (short exposure usually without lasting effects)
1,700 ppm: coughing, bronchospasm, risk of pulmonary edema
2,000 to 3,000 ppm for 30 minutes: potentially fatal

Chronic low-level exposure (such as in poorly ventilated barns or near large livestock operations) is associated with cough, wheeze, reduced lung function, and higher asthma rates in farm workers and nearby residents. Direct contact with concentrated ammonia causes chemical burns to skin, eyes, and respiratory tract.

How it's measured

Ammonia is measured in ppm or micrograms per cubic meter. Key occupational limits:

OSHA PEL: 50 ppm, 8-hour time-weighted average
NIOSH REL: 25 ppm TWA, 35 ppm short-term (15-minute)
ACGIH TLV: 25 ppm TWA, 35 ppm STEL
NIOSH IDLH (Immediately Dangerous to Life or Health): 300 ppm

There is no federal NAAQS for ammonia. Outdoor concentrations in clean rural areas run under 1 part per billion (ppb); near livestock operations they can hit 100 ppb to several ppm. Indoor levels in clean homes are typically under 50 ppb.

What you can do

Use cleaning products in well-ventilated spaces and never mix ammonia-based cleaners with chlorine bleach (that produces chloramine gas). Switch to vinegar-based or oxygen-bleach cleaners for routine work. Keep cat litter boxes in well-ventilated rooms, scoop daily, and change litter regularly.

If you live near a large livestock operation, keep windows closed during peak emission events (often after manure spreading), run HEPA air purifiers (they catch ammonium particles even though they do not capture NH3 gas itself), and report severe odor or health complaints to your state air agency.

For agricultural workers, refrigeration technicians, and anyone working with anhydrous ammonia, follow OSHA training, wear chemical-resistant gloves and goggles, and use a supplied-air respirator for high-concentration work. Cartridge respirators with ammonia cartridges work for low to moderate exposures.

Sources

This article is for educational purposes only. Canairy does not provide medical advice, diagnosis, or treatment. Talk to a qualified health professional about your specific situation.