By Tony Thurmond, CRCST, CIS, CHL, FCS
During initial training, sterile processing (SP) technicians become aware of chemical indicators (CIs). They may see them in a package to be sterilized or one that has already undergone sterilization. It is crucial that CIs are understood, used and interpreted correctly (there is more to it than just seeing a color change).
There are six types of CIs, and each is categorized accordingly (Type 1 through Type 6). The three variables that determine each type of indicator are temperature, exposure time, and steam quality. An indicator using one or more variables is designed to indicate what happened during the sterilization process. Note: The color change of any CI indicates that the product has been exposed to a process, but it is not an indicator that the contents are sterile.
• Type 1 – A Type 1 CI is considered a process indicator, showing that a package or container has been exposed to a steam sterilization process. This type is usually an external indicator, meaning it can be seen outside the package or container. A Type 1 indicator can come in different forms, including indicator tape, indicator label, container indicator card, or a tamper-resistant device such as a lock. Most peel packs have a Type 1 indicator on the peel pouch that will change color when the temperature is increased.
• Type 2 – This type is used for specific test procedures, such as the Bowie-Dick, which checks for evidence of an air leak, leaky seals, or steam supply or steam trap issues. This test should be completed after a warm-up cycle at the beginning of the day. Type 2 indicators are typically packaged in a specially designed pack to simulate a thick barrier of steam penetration. The test indicates how well the sterilizer pulls air from the chamber to ensure effective steam sterilization.
• Type 3 – A Type 3 CI is designed to monitor exposure of a single critical variable, such as temperature or time. Unlike the Type 1 indicator, this type is intended to be placed inside the package to be sterilized. The CI reacts to the variable and undergoes a color change when the required level of exposure to that variable has been reached; however, it does not indicate time or steam quality or provide complete cycle verification.
• Type 4 – A Type 4 CI is an internal indicator designed to react to two or more critical process variables. These are often used for sterilization in clinic settings.
• Type 5 – This type of CI, an integrating indicator, reacts to all critical process variables for various sterilization cycles. This is the most common CI for pack monitoring. Note: This indicator is found in most process challenge devices (PCDs); it is combined with a biological indicator (BI). With a passing BI, a steam load can be released for non-implant and implant-related items.
• Type 6 – This type is also known as an emulating indicator. It is designed to react to all critical process variables for a specified sterilization cycle. These indicators are time-specific and should be used only with that cycle time in mind. For example, a 10-minute Type 6 CI can only be used on 10-minute cycles.
What follows are general guidelines for proper CI use. Regardless of the CI type, proper use requires diligent adherence to the indicator manufacturer’s instructions for use (IFU). Even CIs that appear similar may have different processes or steps in the IFU. Before the products’ use, technicians must read and understand the IFU and recognize what the CI looks like before and after its use. If any questions or confusion about a CI or its IFU arise, the manufacturer should be contacted to provide clarification.
• External CIs – This indicator only indicates that the wrapped package, container, or peel pack has been exposed to a steam sterilization process and does not guarantee sterility. External indicators should not be covered (i.e., do not place a label on top of sterilization tape).
• Internal CIs – Type 5 or Type 6 CIs provide more information about the critical parameters for sterilization; however, it is essential to remember that Type 5 indicators react to all critical parameters across a range of sterilization cycles, and Type 6 indicators react to all critical parameters for only specified cycles. Using a Type 6 for an incorrect cycle would be ineffective. For example, if using a Type 6 CI designed for a 10-minute cycle on a cycle that is only four minutes, the indicator will consider the cycle a failure because the 10-minute cycle requirement would not have been met.
CIs should be placed in an area considered the least accessible to steam penetration to help verify that steam has sufficient contact with items being sterilized. CIs should be placed in a location that allows the user to locate and see the results easily when the tray is opened. Always follow the CI’s IFU to ensure its correct and proper placement and never use tape or other adhesives to secure internal CIs to the inside of a package or tray. Multi-layer trays should have at least one indicator per layer. CIs in different layers might read differently. For example, the indicator on the top layer might have a color change all the way to the end, while another indicator two levels down may have just barely passed the “accept” line.
CONCLUSION
CIs are essential tools for monitoring sterilization parameters and are integral to the tray-building process. Technicians must be knowledgeable about the different types of CIs and what they monitor. They must always follow the products’ IFU to ensure the indicators are placed correctly and their results are interpreted properly. This knowledge can be shared with end users who open the packages at the point of use.
– Tony Thurmond, CRCST, CIS, CHL, FCS, is a sterile processing manager at Dayton Children’s Hospital.
Source: Much of this information was summarized from ANSI/AAMI ST79: 2017/(R)2022 Comprehensive guide to steam sterilization and sterility assurance in health care facilities.
