Abstract: A method and apparatus for generating a non-flammable gaseous mixture from a first flammable gas and a second gas in which said first gas is flammable. Air may be extracted from the atmosphere or storage container to be treated. The air is circulated in a conduit (22) via blower (14). A flammable gas is injected (12) into the conduit where it is rapidly diluted to a level below its flammability limit. The method is suitable for unattended automatic treatment over an extended period of time, or a so-called “one shot/quick dump” fumigation where concentrations and flow rates are much higher and the process is under manual supervision.