Abstract: In a low temperature hydrogen peroxide gas plasma sterilizer, the accurate control of concentration of the hydrogen peroxide sterilant is an important factor in determining reliability and sterilization efficacy of the sterilization process. The present application describes sterilizers, and sterilization methods, which use a novel injector-concentrator arrangement which allows accurate concentration of the sterilant performed concurrently with the sterilization process. This process enables the device to sterilize wide range of sensitive equipment within a shorter sterilization cycle.