Quantitative assessment of the standard method for measuring steam composition in surface sterilisation

Area of Science:

• Medical Devices
• Sterilization Technology
• Quality Control

Background:

• Steam composition, specifically the fraction of non-condensable gases (NCGs), is critical for effective steam sterilization.
• Standard EN 285:2015+A1:2021 provides a method for measuring NCG fraction (NCG%) but lacks detailed specifications for process parameters and environmental conditions.

Purpose of the Study:

• To quantify the impact of unspecified parameters on NCG% measurements.
• To identify factors influencing NCG% variability in steam sterilization testing.
• To propose improvements for a more reliable steam sterilization testing procedure.

Main Methods:

• Sterilization cycles with varying profiles and loads were conducted in a medium-sized steam sterilizer.
• Non-condensable gases and steam condensate volumes were measured at 30-second intervals.
• NCG% values were calculated at different time points and condensate volumes, with theoretical estimation of environmental condition effects.

Main Results:

• NCG% values and test outcomes were significantly influenced by the process profile, load amount, and condensate collection timing/volume.
• Environmental conditions (temperature and pressure) demonstrated a non-negligible impact on NCG% measurements.
• Variability in NCG measurements compromises the reliability of the standard method for sterilizer qualification and steam composition estimation.

Conclusions:

• The lack of detailed specifications in the standard method leads to NCG% measurement variability, impacting sterilizer qualification.
• Real-time, quantitative monitoring of steam composition during production processes is recommended.
• Improved testing procedures are necessary to enhance steam sterilization efficacy and quality assurance.