A safe alternative to ethylene oxide for reprocessing heat-sensitive lumen medical devices, such as endoscopes, is needed. The effectiveness of a new, safe, low-cost, and environmentally friendly low-temperature sterilization process using ozone was assessed.

Rigid lumen devices were used to assess the maximum length of lumens of different internal diameters that can be sterilized in the TSO₃ model 125L ozone sterilizer. Two inoculation techniques were used. An inoculated wire was placed inside lumens with internal diameters of 0.8 mm and larger, whereas lumens with an internal diameter of 0.5 mm were inoculated directly.

Lumens with internal diameters of 0.5 mm, 1 mm, 2 mm, 3 mm, and 4 mm with lengths varying between 45 and 70 cm can be sterilized with ozone. Calculation of the log reduction value for each size demonstrated the achievement of a sterility assurance level of 10⁻⁶. Experimental results demonstrated a linear relationship (with r² = 0.990) between the length of lumen that can be sterilized in the 125L ozone sterilizer and its internal diameter. Effective sterilization of an ACMI ureteroscope that is more challenging in terms of sterilant penetration in a small lumen (0.8 mm) compared with the stated lumen claims confirms that the relationship can conservatively be used to predict the length of a lumen device that can be sterilized in the 125L ozone sterilizer for a given diameter.

Intermediate sizes of lumen devices that can be sterilized in the 125L ozone sterilizer can be interpolated from the linear relationship between diameter and length found in the present study.