A Localized Analysis of the Sterilization Process by Direct Steam Monitoring

Steam sterilization is a standard tool in the field of healthcare and medical equipment as it is economical, effective, and reliable. Considering the increase of antibiotic resistance and the challenge in sterilizing narrow tubes used for keyhole surgery, a safe process control is required. To achieve this, a full understanding of the local dynamics of the sterilization process inside the sterilizer is crucial. In this paper, water condensation under high temperature and high pressure, focusing on sterilization conditions, is qualitatively analyzed. An infrared sensor system was designed supplied by two LEDs, at a steam-absorbing and a non-absorbing wavelength, respectively. The local water vapor concentration was directly detected by evaluating the absorbance of infrared light as it passes through steam. Based on the absorbance monitored by this optical sensor, the condition of the steam was classified with respect to saturation and the onset of condensation. For typical sterilization cycles, differences as well as identical behavior between the local sensor measurements and the global results calculated from the temperature and pressure sensors are discussed.