Anhydrous Ammonia Bulk Storage Regulations (C.R.C., c. 1146)

74 The principal hazards associated with the handling of anhydrous ammonia are as follows:

• (a) mixtures of air and anhydrous ammonia consisting of 16 to 25 per cent by volume of anhydrous ammonia are flammable and may ignite at a temperature as low as 1204°F in the presence of iron. For outdoor installations, this condition is not likely to be obtained except as a result of a tank or pipeline rupture. However, serious fires and explosions have occurred in which anhydrous ammonia was a contributing factor. Anhydrous ammonia becomes slightly unstable at 840-930°F and dissociates into hydrogen and nitrogen. The presence of small quantities of oil or other combustible material in anhydrous ammonia will increase the fire hazard;

• (b) 100 p.p.m. is the maximum average atmospheric concentration of ammonia to which workers may be repeatedly exposed without adverse effect on their health. Exposure to concentrations of 250 p.p.m. for 30 minutes is considered dangerous and an exposure of 30 minutes’ duration to concentrations of 5,000 p.p.m. is considered to be fatal. Industrial gas masks of a type approved for use in ammonia atmospheres should be located in a convenient place. Approximately 400 p.p.m. will cause immediate throat irritation and 700 p.p.m. will cause immediate eye irritation; and

• (c) in addition to the above-mentioned hazards, anhydrous ammonia is shipped and stored under pressure and those general safety precautions prescribed for the handling of compressed gases should be observed.