A method for decontaminating an object disposed in a region. The method includes the steps of: heating the region to a target temperature; introducing steam into the region until a humidity level in the region reaches a target humidity level; introducing a vaporized sterilant into the region until a sterilant concentration in the region reaches a target sterilant concentration; and maintaining the target temperature, the target sterilant concentration and the target humidity level until a predetermine target dose is obtained.