By Gerry O’Dell, O’Dell and Hodge Consulting, and Deborah Havlik, DAHavlik Consulting LLC
The items that can affect the energy transfer are “wet” steam (i.e., too much condensed water in the steam usually caused by contamination in the steam) or steam that is superheated (steam that is too dry because it has been heated beyond its saturation point) creating a dry heat process. Both can result in a lack of sterilization.
Contained product sterilization is where indirect contact of the heating medium with the external surfaces of contained product is used to create moist heat internally to sterilize the product within the container. It is performed using heat transfer methods such as steam or steam-air mixtures, water sprays, or water immersion. For many practitioners, this concept is best described by the method used to sterilize growth media in the microbiology laboratory; in this case the energy transfer occurs by conduction or convection². Healthcare products that can be sterilized using contained product processes are items such as intravenous solutions and dermal fillers.
Moist heat sterilization is a faster sterilization process than dry heat sterilization and typically occurs at lower temperatures for shorter times. However, dry heat sterilization can be a cost-effective, efficient method to sterilize those items that are conducive to the process.
Dry Heat Sterilization
While most often used in the pharmaceutical industry for depyrogenation and thus sterilization of product containers, dry heat sterilization can also be an option for healthcare products that cannot withstand exposure to moisture at high temperatures. This is a simple process; the two parameters of dry heat sterilization are time and temperature. Besides the ISO 20857 standard³, PDA TR.3,4 provides guidance for dry heat processes. Examples of healthcare products sterilized by dry heat include ophthalmic products, silicone implants, wound care products, and dental instruments.
Conclusion
Heat sterilization with either moist or dry heat can be an effective method for sterilization for medical devices that can withstand the temperatures of the process and are common methods of sterilization for other types of health care products. The requirements and guidance for these processes are defined by standards.¹,³
References
[1] ANSI/AAMI/ISO 17665:2024, Sterilization of health care products — Moist heat —Requirements for the development, validation and routine control of a sterilization process for medical devices. Association for the Advancement of Medical Instrumentation; 2024. Arlington, VA.
[2] Technical Report (TR) 1:2007, Validation of Moist Heat Sterilization Processes: Cycle Design, Development, Qualification and Ongoing Control. Parenteral Drug Association; 2007. Bethesda, MD
[3] ANSI/AAMI/ISO 20857:2010/(R)2015, Sterilization of health care products — Dry heat — Requirements for the development, validation and routine control of a sterilization process for medical devices. Association for the Advancement of Medical Instrumentation; 2010. Arlington, VA.
[4] Technical Report No. 3 (Revised 2013) Validation of Dry Heat Processes Used for Depyrogenation and Sterilization. Parenteral Drug Association; 2013. Bethesda, MD.
