Chemical Indicators 101: Applications for Use

November 1, 2004

Chemical Indicators 101: Applications for Use

Chemical Indicators 101: Applications for Use

By John A. Kurowski, BS, RN

Since the first steam sterilizer wascreated by Charles Chamberland in 1880, researchers have worked on methods tomonitor sterilization processes. It was not until the late 1940s and early 1950sthat biological and chemical indicators were used routinely to monitor theprocess. At that time, it was stated that no single quality-assurance monitoringmethod assures that any item is sterile: rather, it assures that the conditionsfor sterilization to occur were met. That very statement remains valid in todayshealthcare environment.

As sterilization processes have evolved and become morecomplex, so have the monitoring systems that we use. Sterility assuranceprograms may consist of the following tools that healthcare management can use:

  • Physical monitoring

  • Chemical indicators/integrators

  • Biological indicators

  • Sterilizer preventative maintenance

  • Loadrecord keeping This article discusses chemical indicators/integrators (CIs).

Chemical indicators are defined by the Association for theAdvancement of Medical Instrumentation (AAMI) as sterilization processmonitoring devices designed to respond with a chemical or physical change to oneor more of the physical conditions within the sterilizing chamber. CIs are oftenused to detect sterilizer malfunction/failures resulting from improper loadingof the sterilizer, incorrect packaging, deficiencies of the sterilizing agent,or malfunction of the sterilizer itself.

Remember, the pass reading of a CI does not mean thatthe item or items in the sterilizer load are sterile; it means that theparameter or parameters for sterilization that the CI was designed to measurehave been met. The use of CIs is only one portion of an effective qualityassurance program. They should be used in conjunction with a biologicalindicator (spore test), physical monitors, a sterilizer preventative maintenanceprogram, and accurate record keeping for each sterilization load.

Chemical Indicator Classifications

AAMI ST-60 defines five classes of CIs and the specificperformance requirements for each.

Process Indicators (Class 1): Themost basic of chemical indicators, they are also known as throughput indicators.These CIs are intended for use with individual items to be sterilized. They aredesigned to demonstrate that the item has been exposed to a sterilizationprocess and to distinguish between processed and non-processed items. Examples of Class 1 indicators are tape and the indicatorsfound on paper or plastic peel pouches.

Indicators for Use in specific Tests (Class 2): Alsoknown as specialty indicators, Class 2 indicators are designed for use inspecific test procedures as defi ned by relevant sterilization standards.Examples of Class 2 indicators are the Bowie Dick and Dart products used insteam sterilizers. These indicators test for the presence of air in the steamsterilizing chamber. A positive test would mean that air, which inhibits theconditions necessary for sterilization, has either not been removed during thecycle or has entered the chamber through leaks in the system. Maintenance mustbe performed on the steam sterilizer to prevent the presence of air in thechamber during a sterilization cycle.

Single-parameter Indicators (Class 3): Theseindicators react to one of the critical process parameters of sterilization andindicate exposure to a sterilization cycle at stated values of the chosenparameter. Critical parameters typically chosen for steam sterilizationprocesses are time or temperature.

Multi-parameter Indicators (Class 4): Theseindicators are more accurate by design than Class 3 indicators. They react totwo or more critical parameters of the sterilization process and indicateexposure to the sterilization cycle at stated values of the chosen parameters. Time and temperature are examples of steam sterilizationparameters, and time and concentration of ethylene oxide are chosen for EOsterilization.

Integrating Indicators (Class 5): Theseindicators, known as integrators, are designed to react to all criticalparameters over a specified range of sterilization cycles. Their performancehas been correlated to the performance of a biological indicator (BI) under itslabeled conditions for use. This class of indicator can be used in place of theBI in many applications, thereby reducing the overall cost of sterileprocessing.

Use of Chemical Indicators

When considering which class of indicator to use, you mustconsider your external and internal chemical monitoring needs for your varioussterilization systems.

External indicators are simply used to distinguish betweenprocessed and unprocessed items. A Class 1 indicator in the form of tape, anindicating label, or the indicator legend on a paper or plastic peel pouch isappropriate and should be placed on each package that is intended forsterilization. The external CI usually exhibits a simple visual color changethat shows the package has been exposed to physical conditions present during asterilization process.

Internal indicators need to be used within each package thatwill be sterilized. Depending on the complexity of the pack and devices withinthem, a Class 3, Class 4, or Class 5 CI can be used. All internal CIs should beplaced in an area of the package that is determined to be the least accessibleto sterilant contact. This may not always be in the center of the package.

AAMI states that a Class 5 indicator may serve as the basisfor the release of processed items, excluding implants.

Integrator challenge packs utilize a Class 5 chemicalintegrator within an appropriate challenge pack to monitor sterilization loads. The challenge packs are placed within the sterilization load,outside the packs, in the sterilization chamber, and have been correlated to thekill achieved in the AAMI 16 towel BI test pack. The result of the chemicalintegrator may be used to release the load, excluding implantable devices.

Results of external indicators and chemical integratorchallenge packs can be read at the end of the sterilization cycle when thepackage is retrieved from the sterilizer. However, internal indicators must beinterpreted at the time of use. Therefore all healthcare personnel should betrained on the proper interpretation of a positive and negative result and whatto do if a negative result occurs.

Be an Informed Consumer

In order to be an educated consumer you must be familiar withthe parameters you wish to monitor, which will help you select the type or classof indicator(s) to purchase. Healthcare management should ask the indicatormanufacturer for reliability data and for the safety and overall performancecharacteristics of their products. Questions to ask include:

  • Are the indicator results easy to interpret?

  • Can you store the indicator results for a period of time?

  • What sterilization parameters will the indicator detect?

  • Is it biologically correlated? If so, what are the specifics (organism, D-value, population)?

  • Does the indicator have a shelf life and what are therequired storage conditions?

By asking these simple questions, you will ensure the correctchoice of indicators to meet your quality assurance needs.

John A. Kurowski, BS, RN, is a global clinical educationmanager for STERIS Corporation. He provides education and training to STERISemployees and healthcare facilities in the areas of infection prevention, theproper use of STERIS products, and proper cleaning, decontamination, andsterilization techniques and procedures. He has been a featured speaker for boththe local and national Association of periOperative Room Nurses (AORN), theAssociation for Professionals in Infection Control and Epidemiology (APIC), andthe Society for Gastroenterology Nurses and Associates (SGNA). He is an activemember of these organizations.