Circulation system for biocidal gas

In the treatment of articles with a sterilant gas such as an alkylene oxide, and the circulation of the gas throughout a treatment chamber containing the articles to be treated, a gas circulating system completely devoid of electrical contacts, switches, electrical motors and other potentially dangerous electrical components which could cause explosive ignition of the sterilant gas. The circulation system includes a fluid-driven turbine-like impeller completely isolated from the sterilant gas, and drivingly coupled to a fan blade which serves to force the gas through conduits and to circulate and recycle the sterilant gas throughout the treatment chamber. In a second embodiment of the invention a magnetically coupled drive is used to actuate the sterilant-circulating fan.