General chemical information and human exposure limits

Common Name: Anhydrous Ammonia

Anhydrous is a term that identifies the chemical is without water. Terms used for ammonia in water are aqua ammonia, ammonium hydroxide or ammonia liquor. Ammonia in water has properties vastly different than those of anhydrous ammonia and the two should not be confused.

Synonyms:

R717, Spirit of Hartshorn, nitro-sil, am-fol, liquid nitrogen. It is sometimes referred to as 82-0-0 where 82 refers to the percent of nitrogen fertilizer provided.

Chemical Name: Ammonia

Chemical Family: Alkali

An alkali is a base that produces hydroxide ions ( OH- ) when dissolved in water. Bases are typically water-soluble and always have a pH greater than 7 when in solution.

Chemical Formula: NH3

The ammonia molecule consists of one atom of nitrogen (N) and three atoms of hydrogen (H). It is produced by combining atmospheric nitrogen which constitutes 78% of the air we breathe with hydrogen. This nitrogen fixation requires high temperature and pressure in the presence of an iron catalyst.

Composition

Consists of greater than 99% ammonia with the remainder being water. The CAS number assigned to ammonia by the American Chemical Society is 7664-41-7.

Appearance and odor

The liquid and gas are colorless. The white cloud you observe during an ammonia release is the ammonia freezing the water droplets in the air to ice. Gas has a penetrating, pungent, suffocating odor

United Nations (UN) identification number: 1005

Human Exposure Limits

People working with ammonia may become desensitized and not be able to detect ammonia at low concentrations. Also, exposure levels which are tolerated by the average person may cause respiratory damage to others. The concentrations below are from ammonia in air by volume.

Least Perceptible Odor

  • 1 to 5 parts per million (ppm).

Odor Threshold

  • Fortunately, ammonia has an odor threshold of about 20 ppm which is substantially below the IDLH (see below) so most people will seek relief well below that which would cause adverse health affects.

Recommended Exposure Limits or RELs

  • Time-weighted average concentrations for up to 10-hour workday during a 40-hour workweek is 25 ppm or 18 mg ammonia per cubic meter of air.

Short-term Exposure Limit or STEL

  • 15 minute time weighted average that should not be exceeded at any time during the work day is 35 ppm or 27 mg ammonia per cubic meter of air.

No discomfort or impairment of health for prolonged exposure

  • 50-100 ppm. During a short exposure at 150 to 200 ppm a person will experience general discomfort and eye tearing with no lasting effects.

Immediately Dangerous to Life and Health or the IDLH

  • IDLH is a maximum concentration of ammonia at which a worker could escape without injury or irreversible health effects. The IDLH for ammonia is 300 ppm. A short exposure of 400-700 ppm will cause severe eye, ear, nose and throat irritation but with no lasting effects.
  • Coughing and bronchial spasms will occur at 1700 ppm.
  • 30 minute exposure at 2000 to 3000 ppm may be fatal.
  • Rapidly fatal due to serious edema, strangulation, and asphyxia at 5,000 to 10,000 ppm. Fatal at 10,000 ppm or 1% by volume.

Skin Sensitivity

  • Vapor concentrations of 10,000 ppm (1%) are mildly irritating to the moist skin while 30,000 + ppm may cause skin burns.