Hazards of Anhydrous Ammonia

Anhydrous (waterless) ammonia (NH3) is formed by the combination of the two gaseous elements, nitrogen and hydrogen. Liquid ammonia is colorless; it boils at a temperature of -28° F at atmospheric pressure and freezes to a white crystalline mass of -107° F. Gaseous ammonia is also colorless and has an extremely sharp, penetrating, pungent, and unpleasant odor.

Concentrated ammonia is both toxic and flammable and must be considered extremely dangerous. It is imperative that all persons handling ammonia be thoroughly familiar with the hazard involved. Although ammonia is sometimes classified as a non-flammable compressed gas, the gas is flammable in air in comparatively high concentrations (16 to 25 percent by volume).

Since ammonia has a penetrating, suffocating odor, and is strongly irritating, it is not likely that a person will voluntarily remain in a contaminated atmosphere. Irritation to the eyes, respiratory tract, and throat results from concentrations as low as 0.05 to 0.1 percent. A concentration of 0.2 percent produces convulsive coughing and may be fatal after an exposure of less than one-half hour. Ammonia gas in a concentration of 0.6 to 1.0 percent volume is lethal within a few minutes. The maximum concentration tolerated by the skin for more than a few seconds is 2 percent. Concentrations on the order of 50 parts per million (0.005 percent) can be detected by the average person.

Ammonia, either as an anhydrous liquid or gas, is a strong irritant, capable of inflicting severe irritation to the surface, tissues of the eyes, nose, throat, and lungs. One of the most hazardous effects of ammonia is its effect on the eyes. When the eye is sufficiently exposed to ammonia, the iris becomes congested and hemorrhaging begins, often resulting in permanent blindness.

In addition to its caustic action, liquid ammonia may cause severe injury to the skin by freezing the tissue. If handled improperly, liquid ammonia can cause irreparable damage, or death.

Canister-type industrial gas masks with full face pieces are adequate protection where ammonia concentration does not exceed 3 percent. For emergencies, or where concentrations exceed 3 percent, a closed-system supplied-air respirator with a full face piece should be used.