Abstract: Sterilization apparatus includes a monitoring system capable of continuously monitoring levels of a sterilant, such as hydrogen peroxide vapor. The monitoring system includes a sensor chamber joined in fluid communication with a sterilant supply conduit of the sterilization apparatus. A gas-detecting semiconductor sensing element, and associated temperature sensor, are provided within the sensor chamber to provide output signals corresponding to detected levels of sterilant. The sensor chamber isolates parametric influence, such as relative humidity, temperature and flow rate, to provide more accurate concentration level readings. A data collection circuit is operatively coupled to the sensors to provide an output corresponding to detected levels of sterilant within the apparatus.