A decontamination system for decontaminating a region with a vaporized decontaminant, such as vaporized hydrogen peroxide. The concentration of the vaporized decontaminant within the region is modified in response to operating conditions. The decontamination system adjusts the concentration of the vaporized decontaminant in response to the monitored saturation concentration of the decontaminant, thereby preventing condensation of the vaporized decontaminant during a decontamination cycle. The decontamination system also adjusts the concentration of the vaporized decontaminant in order to minimize the time required to complete a successful decontamination operation.