By: Pamela H Caudal, RN, CNOR, CSPDS, ACSP

Chemical indicators have been around as long as life itself. For example, hydrangeas bloom blue in acidic soil and pink in basic soil so they are an excel lent indicator of soil conditions. That being said, chemical and biological indicators were not used routinely until the late 1940s and early 1950s to monitor sterilization processes. At that time, it was stated no single quality-assurance monitoring method assures that any item is sterile; rather it assures the conditions for sterilization to occur have been met. This statement is still true in today’s sterilization practices. Chemical indicators are either physical or chemical devices used to monitor one or more of the process parameters of the sterilization cycle. Currently they are divided into 6 classical cations. They are as follows: a. Class 1: Process indicators are intended for use with individual items, e.g., containers, to indicate that the unit has been directly ex posed to the sterilization process and to distinguish between processed and non processed items. Indicator tapes, indicator

labels and load cards are examples of externally visible chemical indicators that are on the outside on the packages. b. c. d. e. Class 2: Indicators are intended for use in specific test procedures as defined in relevant sterilizer/ sterilization standards. . Bowie-Dicks are one type of specific testing most are familiar with. These are used to show the efficacy of air removal and steam penetration. Class 3: A single Kari able indicator that is designed to solely show the exposure to one sterilization process at a stated value (SV) of the chosen variable. One example of a single variable is a temperature tube that houses a chemical pellet which melts at a specific temperature. Class 4: These are considered as multiple variable indicators. They are designed to react with two or more of the critical variables and are intended to indicate exposure to a sterilization cycle at IVs of the chosen variable. Examples of these class 4s would be the paper strips with a color change chemical indicator. These are usually used in side each package. Class 5: Integrating indicators are designed to react with all critical Kari able. These can be used as internal chemical indicators in all packs and containers for pack control monitoring. They can also be used as an additional monitoring tool in order to be able to release loads that do not contain im plants based on the appropriate Process Challenge Device. These indicators can also be used in implant loads IF a Biological Indicator is run with the class 5 integrator. The load can NOT be re leased until the BI result is known except in emergencies. f. Class 6: These are called emulating Indicators which are cycle verification indicators which are designed to react to all critical variables for specified sterilization cycles. In other words they are considered to be indicative of a complete cycle by showing the presence or absence of specific time and temperature parameters during a cycle. They are currently only available in the US for steam sterilization. Chemical indicators are convenient, are inexpensive, and indicate that the item has been exposed to the sterilization process. In one study, chemical indicators were more likely than biological indicators to inaccurately indicate sterilization at marginal sterilization times (e.g., 2 minutes).