NH,. A colourless, pungent smelling gas which liquefies at 15 C at a pressure of 7. 4 atmospheres. Slightly lighter than air. Very soluble in water. Not readily flammable but can form explosive mixtures in air if heating and/or compression takes place. It is used extensively as a refrigerant, also in the chemical, explosives, petroleum refining, fertiliser, metallurgical and many other industries. Storage and transport can be in glass Winchesters and steel drums as a 33 per cent ammonia/water solution or in steel cylinders as a pressurised liquid. Dangerously high internal pressure in storage cylinders can be developed as a result of a comparatively slight increase in temperature. Not readily flammable but will burn vigorously in oxygen and under certain conditions ammonia/air mixtures can be exploded by an electric spark. Breathing apparatus with protection should be worn for firefighting and high concentrations may require fully-protective clothing. If unable to remove the cylinders from the source of heat keep them cool by the use of spray jets played along the full length of the cylinders. High level ventilation as soon as fire situation tactics permit. Water spray jets should be used to clear the atmosphere as the gas is very soluble in water