Chemical Indicator
What is the chemical indicator and bowie dick test packChemical indicator 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 classifications. They are as follows:Class 1: Process indicators are intended for use with individual items, e.g., containers, to indicate that the unit has been directly exposed to the sterilization process and to distinguish between processed and no processed items. Indicator tapes, indicator labels and load cards are examples of externally visible chemical indicators that are on the outside on the packages.
Class 2: Indicators are intended for use in specific test procedures as defined
in relevant sterilizer/ sterilization control 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 variable indicator that is designed to solely show the
exposure to one Sterilization control products 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 SVs of the chosen variable.
Examples of these class 4 would be the paper strips with a color change
chemical indicator. These are usually used inside each package.Class 5: Integrating indicators are designed to react with all critical
variables. 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
implants 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 released until the BI result is known
except in emergencies.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 indicator 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).Steam Chemical indicators should be used in conjunction with biological
indicators, but based on current studies should not replace them because they
indicate sterilization at marginal msterilization time and because only a
biological indicator consisting of resistant spores can measure the microbial
killing power of the sterilization process. Chemical indicators are affixed on
the outside of each pack to show that the package has been processed through a
sterilization cycle, but these indicators do not prove sterilization has been
achieved. Preferably, a chemical indicator also should be placed on the inside
of each pack to verify sterilant penetration. Chemical indicators usually are
either heat-or chemical sensitive inks that change color when one or more
sterilization parameters (e.g.,steam-ime, temperature, and/or saturated steam;
ETO-time, temperature, relative humidity and/or ETO concentration) are
present.Chemical indicators have been grouped into five classes based on their ability
to monitor one or multiple sterilization parameters. If the internal and/or
external indicator suggests inadequate processing, the item should not be used
An air-removal test (Bowie-Dick Test) must be performed daily in an empty dynamic-air-removal
sterilizer (e.g., prevacuum steam sterilizer) to ensure air removal. The
definitions listed above were taken from the ANSI/AAMI/ISO 11140-1:2005
definitions.Definitions:Chemical indicator evice
for monitoring a sterilization process. The device is designed to respond with
a characteristic chemical or physical change to one or more of the physical
conditions within the sterilizing chamber. Chemical indicators are intended to
detect potential sterilization failures that could result from incorrect
packaging, incorrect loading of the sterilizer, or malfunctions of the
sterilizer. The "pass" response of a chemical indicator does not prove the item
accompanied by the indicator is necessarily sterile. The Association for the
Advancement of Medical Instrumentation has defined five classes of chemical
indicators: Class 1 (process indicator); Class 2 (Bowie dick test pack indicator);
Class 3 (single-parameter indicator); Class 4 (multi-parameter indicator); and
Class 5 (integrating indicator).