ISO 11140 Sterilization of Health Care Products - Chemical Indicators

The “ISO 11140 Sterilization of health care products - Chemical indicators” standard published by the International Organization for Standardization (ISO) consists of the following subsections published under the same title:

• “ISO 11140-1 Part 1: General requirements"standardThe general requirements and test methods for indicators that indicate exposure to sterilization processes through physical and chemical changes of substances and are used to monitor the achievement of one or more process parameters specified for a sterilization process are described.

Their effects are not dependent on the presence or absence of a living organism. Biological test systems are considered test systems whose interpretation depends on demonstrating the viability of an organism. Such test systems are addressed in the ISO 11138 series of standards for biological indicators.

The requirements and test methods described in this standard apply to all indicators specified in other parts of ISO 11140, but when a requirement is replaced or supplemented by a subsequent part, the requirement of that part prevails.

Sterilization is a critical process in healthcare and laboratory environments, ensuring that medical instruments and materials are free of viable microorganisms. The ISO 11140-1 standard plays a vital role in verifying the effectiveness of sterilization processes through chemical indicators.

The ISO 11140-1 standard is an international standard that defines general requirements for chemical indicators used in sterilization processes. These indicators are tools that help healthcare professionals confirm whether products have been exposed to the correct sterilization conditions.

Chemical indicators are often used in conjunction with physical monitors (e.g. pressure and temperature gauges) and biological indicators to provide multi-layered assurance that sterilization has occurred correctly.

Chemical indicators are designed to visually verify that one or more of the conditions required for effective sterilization have been met, such as time, temperature, and the presence of a sterilizing agent (e.g., steam, ethylene oxide, or hydrogen peroxide).

They do not prove sterility, but serve as process indicators that help prevent the use of improperly sterilized instruments.

• The “ISO 11140-2 Part 2: Test equipment and methods” standard was later withdrawn and replaced by “ISO 18472 Sterilization of healthcare products - Biological and chemical indicators - Test equipment”.
• The standard "ISO 11140-3 Part 3: Class 2 indicators for steam penetration test sheets" describes the requirements for chemical indicators for use in steam sterilizer steam penetration testing of packaged products (e.g., instruments and porous materials). The indicator to be used for this purpose is a Class 2 indicator, as described in ISO 11140-1. Indicators conforming to ISO 11140-3 are designed for use with the standard test suite, as described in EN 285. ISO 11140-3 does not detail the requirements for the standard test suite, but specifies the performance of the indicators.

Sterilization plays a critical role in preventing infection and ensuring patient safety in healthcare. ISO 11140-3 is a key international standard that defines the requirements for chemical indicator systems specifically used to test steam penetration in vacuum-assisted steam sterilizers.

These tests are necessary to verify that a sterilizer can evacuate air and allow steam to penetrate through the load, a critical factor for successful sterilization.

This standard ensures the reliability of chemical indicator systems used in steam penetration testing. By clearly defining performance and design criteria, it supports daily sterilizer validation and enhances safety and compliance in healthcare environments. Facilities that integrate systems compliant with this standard into their sterilization monitoring protocols demonstrate a strong commitment to quality assurance and infection prevention.

• The standard "ISO 11140-4 Part 4: Class 2 indicators as alternatives to the Bowie and Dick-type test for the determination of steam penetration" describes the performance of a Class 2 indicator to be used as an alternative to the Bowie and Dick-type test for steam sterilizers for packaged healthcare products (instruments and porous loads). The Bowie and Dick-type test is used for routine testing of steam sterilizers and validation of steam sterilization processes.

An indicator conforming to this standard incorporates a specific material used as a test load. This test load may or may not be reusable. This standard does not specify test load requirements, but specifies the performance of the indicator in conjunction with the test load with which it is intended to be used. The indicator specified in this standard is intended to detect poor steam penetration, but does not necessarily indicate the cause of such poor steam penetration. This standard does not include test methods for determining the suitability of these indicator systems for use in sterilizers where the air evacuation phase does not include evacuation below atmospheric pressure.

Sterilization processes in healthcare environments must be strictly controlled and regularly tested to ensure the effectiveness of microbial inactivation. A critical aspect of steam sterilization, particularly in prevacuum sterilizers, is ensuring adequate air removal and proper steam penetration into porous loads.

Traditionally, this was done using the Bowie and Dick test, a daily performance test designed to evaluate the effectiveness of steam penetration and air removal. However, modern standards and technologies offer alternative testing methods. Among these, ISO 11140-4 provides a specific Class 2 chemical indicator system that can serve as a reliable alternative to the traditional Bowie and Dick test.

ISO 11140-4 outlines requirements for alternative chemical indicator systems specifically designed for use in prevacuum steam sterilizers. This standard recognizes the need for high-performance, consistent, and reproducible test devices that are generally easier to use and interpret than traditional test packs made of textile or paper layers.

According to ISO 11140-1, Class 2 indicators are used in specific tests rather than routine sterilization monitoring. ISO 11140-4 applies this class to specialized chemical indicator systems that simulate a challenging porous load, similar to a traditional Bowie and Dick package.

The traditional Bowie and Dick test includes:

• A stack of folded towels or paper towels
• A chemical indicator sheet in the middle
• Placement in an empty sterilizer chamber
• Run a short cycle (typically 134 degrees for 3,5 minutes)

In contrast, chemical indicator devices compatible with the ISO 11140-4 standard,

• Commercially produced test suites or devices.
• Designed for consistent build and performance.
• Validated to simulate the performance of the original Bowie and Dick test.

Using Class 2 indicators compliant with the ISO 11140-4 standard as an alternative to the Bowie and Dick test offers several advantages:

• Greater consistency: Factory-built devices reduce variability due to human error or inconsistent materials.
• Simplified workflow: No need to combine textile test suites.
• Enhanced sensitivity: Designed to detect smaller deviations in vapor penetration performance.
• Clear interpretation: Indicators provide sharp, color-contrasted results that are easier to interpret and document.

The air purge test is used to evaluate the effectiveness of air purge during the prevacuum phase of a prevacuum sterilization cycle or during the pulse phase of positive pulse cycles when non-condensable gases are present in the steam. Air retention due to an inefficient air purge phase, or air leakage or the presence of non-condensable gases during the air purge phase, are conditions that may lead to test failure.

The difference between the steam penetration test (ISO 11140-3 and ISO 11140-4 standards) and the air release test (ISO 11140-5 standard) is “ISO 15882

Sterilization of health products - Chemical indicators - Guide for selection, use and interpretation of results” standard.

Steam sterilization is widely used in healthcare due to its effectiveness, safety, and efficiency. However, its reliability, especially in vacuum-assisted (pre-vacuum) steam sterilizers, depends on the integrity of the sterilizer chamber. Any leaks in the system can introduce air and disrupt the sterilization process.

To ensure airtight performance, sterilizers must undergo regular leak tests, and this is where ISO 11140-5 comes in. This standard specifically defines the requirements for Class 2 chemical indicators used to detect air leaks in steam sterilizers.

The presence of residual air or the continuous introduction of air during the sterilization cycle can create air pockets that prevent steam from contacting all device surfaces. This can lead to incomplete sterilization, posing a serious risk of infection.

Leak testing is typically performed through a vacuum leak test cycle, performed daily or after sterilizer maintenance. This test uses ISO 11140-5 standard indicators to detect leaks in the sterilizer chamber or piping.

• The standard “ISO 11140-6 Part 6: Type 2 indicators and process difficulty devices for use in the performance testing of small steam sterilizers” describes the performance requirements and test methods for hollow and porous devices and the chemical and biological indicators used in these devices to test a specific steam penetration performance of type B cycles and some type S cycles of small steam sterilizers according to the EN 13060 standard.

The hollow and porous devices described in this standard are not intended for use as replacement devices for hollow and porous medical devices used in healthcare facilities.

The chemical indicators used in conjunction with a porous device specified in this standard are designed to demonstrate the adequacy of steam penetration into a porous device in small steam sterilizers.

This standard specifies requirements for:

• A reference porous device, i.e. a textile test suite in which vapour penetration is assessed by thermometric methods, as a reference device against which alternative porous indicator systems can be shown to be equivalent in performance to this standard.
• An alternative porous chemical indicator system with equivalent performance to the reference porous device, i.e. an alternative porous indicator system of any design, usually commercially produced

The chemical indicators used with the hollow load device specified in this standard are designed to demonstrate the adequacy of steam penetration into a narrow lumen (formerly known as hollow load A) in small steam sterilizers.

This standard specifies requirements for:

• A reference porous device, i.e. a lumen device with an attached capsule, in which vapor penetration is assessed by inactivation or survival of a specified biological indicator, is used as a reference device in this standard.
• An alternative hollow device:
  • A lumen device with an attached capsule that uses the same specific test load as defined for the reference hollow device and a chemical indicator specifically designed for use on the reference hollow test load, i.e., vapor penetration is assessed by visual inspection of a chemical indicator.
  • An alternative hollow device of any design, equivalent in performance to the reference porous device, i.e., usually commercially produced.

Ready-to-fill glass barrels and sterilized bottom-assembled syringes, plunger stoppers and plastic barrels for injectable drugs are covered in ISO 11040-4, ISO 11040-5 and ISO 11040-6 standards.

The ISO 11607-2 standard addresses the validation requirements of sealing and packaging processes for medical devices.

Our organization, which has been serving for many years and meticulously following global developments in science and technology, employs a skilled team and extensive infrastructure to conduct testing, measurement, and analysis in a wide range of areas for businesses across all sectors. In this context, we also provide testing services in accordance with the ISO 11140 "Sterilization of Healthcare Products - Chemical Indicators" standard.