Abstract: In a method and an apparatus for recovering a sterilizing gas, in particular ethylene oxide (ETO), materials to be sterilized are sterilized in a sterilizing chamber with a sterilizing gas and a gas flow is withdrawn from the sterilizing chamber. At least part of the sterilizing gas contained in said gas flow is liquefied and separated. The gas flow freed from liquefied sterilizing gas is returned to the sterilizing chamber whilst at the same time at least a part of the separated sterilizing gas is replaced by addition of inert-rendering gas, reducing the concentration of the sterilizing gas in the sterilizing chamber.