Steam Quality Testing

The quality of the steam feeding an autoclave is an important factor in steam steriliza­tion. Like temperature, pressure, and time – steam is a critical variable in the success and repeatability of the sterilization process. As such, steam quality should be part of the validation of any steam sterilizer.

Steam quality is defined as the measurable physical aspects of steam used for sterilization. These physical aspects include temperature (superheat), dryness (liquid water content), and non-condens­able gas content. (Steam quality is not a measure of the impurity content of the steam.) Deviations from established ranges of these aspects of the steam can result in the following issues:

• Wet loads
• Damaged loads
• Unsterile loads
• Sterilization (biological and chemical) indicator failures
• Staining and corrosion of instruments and containers

Each of these issues has a specific cause or causes and can usually be remedied.

 

What to Know About Steam Quality

Almost every sterilizer manufacturer recommends “97% pure steam”. In general, this is not defined, rarely measured, and, if discussed at all, is relegated to the mythology of sterilizer arcana. The good news is that essentially all laboratory and medical autoclaves on the market today can provide sterile, dry, and intact sterilization loads if provided good quality steam from the steam supply. The bad news is that any autoclave can experience the above problems, and the cause is not always some­thing that can be predicted.

With careful design, following well-established principles, and proper maintenance, the system (steam supply and sterilizer) can be engineered to provide a large margin of security against steam quality noncompliance. For a production or GMP environment, steam quality testing should be part of annual preventative maintenance and qualification testing.