A properly sealed sterilization chamber is fundamental to maintaining the required ethylene oxide concentration and pressure conditions throughout the cycle. The following leak tightness tests are performed on an empty chamber to detect any unacceptable leakage that could compromise sterility assurance or operator safety. These procedures align with the performance validation protocols for industrial ETO sterilizers.

General Test Requirements

All leak tests must be conducted with an empty sterilization chamber. After an automatic test cycle completes, filtered air is introduced until the chamber pressure returns to within ±5 kPa of ambient atmospheric pressure. For non-automatic test methods, equivalent provisions must be made to achieve the same pressure equalization before proceeding with measurements.

If required, a stabilization period of 300s ±10s may be set before pressure monitoring begins. During this time, all valves connected to the chamber are closed and the vacuum pump (if used) is stopped. The subsequent observation period for pressure change must be no less than 600 seconds to reliably detect any leakage trends.

Negative Pressure Leak Test

The negative pressure leak test evaluates the chamber’s ability to hold vacuum, which is critical for the evacuation phases of a sterilization cycle. The test pressure should not exceed the lowest set pressure of any sterilization cycle, или -75 кПа, whichever is lower. This ensures the chamber is tested under the most demanding vacuum conditions it may experience in service.

Procedure: Evacuate the empty chamber to the specified negative test pressure. Close all valves connected to the chamber and stop the vacuum pump completely. After the optional stabilization period of 300s ±10s, monitor and record the pressure continuously for a minimum of 600 seconds. The pressure rise over this period must not exceed the allowable leak rate specified in the sterilizer’s performance documentation. Any increase beyond the limit indicates a potential breach in chamber integrity that must be investigated and corrected before the sterilizer is placed into service.

Positive Pressure Leak Test

The positive pressure leak test verifies the chamber’s ability to contain elevated pressures without leakage. The test pressure must be no lower than the highest set pressure of any sterilization cycle, ensuring the chamber is evaluated under worst-case positive pressure conditions.

Special considerations for heated chambers: If the test is performed in a heated chamber, temperature variations can influence pressure readings and affect the calculated leak rate. Поэтому, after reaching the test pressure, a stabilization period must be observed until the temperature stabilizes, plus an additional 120 seconds, before the monitoring phase begins. This compensates for any pressure changes caused by thermal effects.

With all valves closed and the pressure source isolated, record the pressure for at least 600 seconds. The pressure decrease during this period is evaluated against the specified leak rate limit. Consistent monitoring ensures that even minor leaks are detected and addressed promptly.