1 It is believed that compliance with these Regulations will provide a high degree of safety in the storage of ammonium nitrate. Effective implementation of these requirements is most likely to be realized if the persons involved in the storage operations have a good knowledge and understanding of the properties and hazards of ammonium nitrate.
2 The principal properties and hazards of ammonium nitrate are as follows:
(a) ammonium nitrate is an oxidizing material that, at elevated temperatures, will support the combustion of materials such as wood, paper, fuel oil and sulphur; but self-sustaining burning reactions are not usually obtained unless more than one per cent of combustible material is present;
(b) ammonium nitrate undergoes thermal decomposition when heated to temperatures above about 150°F and, under certain conditions, some of which are mentioned below, this decomposition may become dangerous; because ammonium nitrate is usually stored in very large quantities, it has the potential to escalate an ordinary fire into an event approaching disaster proportions and for this reason, even a very small probability of occurrence cannot be ignored;
(c) it is important that ammonium nitrate be adequately separated from combustible materials and that the risk of fire be kept at as low a level as practicable;
(d) mixed fertilizers containing not more than 60 per cent ammonium nitrate as the only oxidizing material, with the balance as inert material, are not usually considered to be either a fire or an explosion hazard in storage; but certain additives or diluents may render even mixed fertilizers as hazardous or more hazardous than pure ammonium nitrate; for this reason, the exemption of a mixed fertilizer from compliance with the requirements of the Commission will depend on the nature and quantities of the ingredients in the mixture;
(e) it has been demonstrated in laboratory experiments that when the decomposition gases are sufficiently confined, they will accelerate or otherwise promote the decomposition reaction; this confinement may be obtained by accident, such as by the collapse of a building;
(f) two of the decomposition gases, nitrous oxide and ammonia, when mixed with certain other gases such as carbon monoxide, are capable of exploding; such explosions may be of sufficient power to detonate the ammonium nitrate;
(g) provisions should be made in the design of storage buildings for adequate ventilation in the event of a fire;
(h) small quantities of iron oxide, chromic oxide and some of the inorganic salts of chromium, copper and manganese are known to enhance or activate the decomposition of ammonium nitrate; it has also been determined that some of the powdered metals such as zinc, magnesium, tin and copper will react with ammonium nitrate to form compounds which are sensitive to impact;
(i) fortunately, the precautions which must be taken to keep the storage hazards of fertilizer grade ammonium nitrate and ammonium nitrate mixed fertilizers within acceptable bounds are relatively simple; it is believed that compliance with the storage requirements of the Commission will sufficiently reduce the explosion hazard of ammonium nitrate so that this hazard need not be allowed for in the safety distance requirements;
(j) water is the only known satisfactory extinguishing agent for an ammonium nitrate fire and should be available near the storage facility in large quantities for immediate use;
(k) as an ammonium nitrate fire progresses, large quantities of very toxic gases are evolved which make it impossible for fire fighters to remain in the vicinity of the fire, unless they are equipped with self-contained breathing apparatus;
(l) all occupied buildings within the vicinity of an ammonium nitrate fire should be evacuated promptly; and
(m) for further information on this subject, the reader is referred to the National Fire Protection Association, 60 Batterymarch Street, Boston, Massachusetts, 02110, or to the nearest ammonium nitrate producer.
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