There was demonstrated possibility of exhaust (purging, armored, ventilation) gases purification from ammonia by means of its catalytic decomposition. There was investigated dynamics of nickel-aluminium catalyst in the flow of ammonia gas. There was examined catalytic activity of catalyst in the process of ammonia cracking in the range of 500-700oC, space velocity 500-5000 h-1 andpressure of process 0.125 MPa. There was specified that at temperature more than 570oC the process of ammonia decomposition is carrying out nearly at equilibrium conditions. There was demonstrated that required for resolve of environmental issues of degree of ammonia conversion attained depending on space velocity value in the range of 570-700oC. Conservation of high values of mechanical strength and total specific area provides long-term exploitation of catalyst in industrial conditions.