Proper monitoring of office sterilizers

May 1, 2007
Question: My office has had a series of “discussions” concerning placement of heat indicators on instrument bags.

by Charles John Palenkik, MS, PhD, MBA

Question: My office has had a series of “discussions” concerning placement of heat indicators on instrument bags. We need a third party to help us do the right thing.

Answer: Proper monitoring of office sterilizers involves a combination of three methods - mechanical, biological, and chemical. Mechanical monitoring involves observation of sterilizer gauges and displays and the recording of unit temperatures, pressure, and exposure times. Ideally, mechanical monitoring should occur with each load. A correct reading does not guarantee sterilization; however, an incorrect reading could be the first indication that problems may exist. Some sterilizers have attached printers that provide a hard copy record of operational parameters during a given run.

Biological monitoring (spore testing) is the main guarantee of sterilizer performance. The technique uses highly heat-resistant bacterial spores. Biological indicators (BIs) come in various forms and contain spore types most resistant to either moist or dry heat sterilizing conditions. After completion of a cycle, BIs undergo culturing to determine if killing of the spore challenge occurred. While most offices use some type of mail-in spore testing service, there are kits for in-house testing of steam autoclaves. Biological monitoring should be a weekly event when normal length cycles are used. A BI should be present in each flash sterilization load, and in any load that contains an implantable device. Failure to kill BI spores is a significant event, which requires immediate action to better assure patient safety.

Chemical monitoring uses heat-sensitive chemicals to assess physical conditions present during the sterilization process. These indicator chemicals change color and/or form when exposed to certain temperatures. Examples include autoclave tape, special markings on instrument bags, and pouches as well as tubes of colored materials. There are two basic types of chemical indicators - exterior and integrated.

Exterior chemical indicators are present somewhere on the outside of a pack, pouch, or cassette wrap. Today, chemicals embedded into packaging or wrapping material are common and inexpensive. Change in appearance (e.g., a color change from light gray to dark black) indicates instrument processing. This helps prevent accidental use of unprocessed items. External indicators do not assure that the contents are indeed sterile, or that a complete sterilization cycle has occurred. Color change is in response to exposure to a specific temperature only.

Integrated indicators change color or form more slowly than do the external types. They respond to a combination of operational factors (e.g., temperature and time) rather than just temperature alone. Placement of integrated indicators is usually inside of packs, pouches, or wrapped cassettes.

In its 2003 infection control guidelines, the Centers for Disease Control and Prevention (CDC) recommended that critical patient-care items require sterilization by heat between patient use. Critical patient-care items penetrate soft tissue, contact bone, and enter into or contact the bloodstream or other normally sterile tissue. Critical patient-care items have the greatest potential for transmitting infection. Packaging after cleaning of instruments, devices, or equipment is an essential step in proper instrument processing. Unwrapped items have no practical shelf-life. Contamination can occur after exposure to the environment or through handling.

The CDC recommends that all packages and wrapped cassettes placed into a sterilizer should have a chemical indicator on the inside. This will confirm that sterilizing heat and/or chemicals have reached the interior of the package (a somewhat greater challenge). Some types of packaging or wraps do allow you to view the inside. In these cases, the chemical indicator needs to be on the outside as well as the inside of the package. The exterior chemical indicator differentiates processed items from those not yet processed. The interior indicator reports penetration of the killing agents.

The Organization for Safety and Asepsis Procedures is a global dental organization dedicated to promoting infection control and safety policies and practices supported by science and research. OSAP helps dental practitioners close the gap between policy and practice by providing helpful publications, educational tools, and programs. OSAP has produced an informative manual that specifically addresses the 2003 CDC infection control guidelines - “From Policy to Practice: OSAP’s Guide to the Guidelines.” Additional information about the manual, as well as other information concerning instrument packaging and wrapping including chemical monitoring, is available on the OSAP Web site at

Dr. Charles John Palenik is an assistant director of Infection Control Research and Services at the Indiana University School of Dentistry. Dr. Palenik has authored numerous articles, book chapters, and monographs, and is the co-author of the popular “Infection Control and Management of Hazardous Materials for the Dental Team.” In 2003, he was chairman of the Executive Board of OSAP, dentistry’s resource for infection control and safety. Questions about this article or any infection-control issue may be directed to [email protected].

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