Abstract: In order to pest control tobacco there is provided in a gas tight tobacco storage room an inert O.sub.2 lacking atmosphere with O.sub.2 between 0 and 5%, CO.sub.2 between 1 and 20% and the balance N.sub.2. This atmosphere is maintained until mortality of the pest. The system for providing this atmosphere includes essentially a generator, which can be a combustion chamber (1) associated with a catalytic chamber (2) (in the case of an open circuit system in which air is drawn from the atmosphere) or a catalytic chamber alone (in the case of a closed circuit system in which air is drawn from the tobacco storage room itself) and a cooling tower (3).The system is generally provided also with an evaporator (5) and a condenser (6) to control the humidity of the inert atmosphere, and a heat exchanger (7) in which the combustion heat is utilized to heat the inert atmosphere at a temperature which speeds up the mortality of the pest.