Abstract: A diazo copier having an exposure section, an ammonia developer section, a copy degassing section, and an enclosed copy receptacle. To develop an exposed copy, it is contacted with ammonia vapors in the development section. The ammonia vapors absorbed by the copy material are released by heating the copy to an elevated temperature in the degassing section from which the copy is deposited in the enclosed receptacle. The released ammonia vapors are removed from the copy by circulating a stream of air through the receptacle and around the copy.