Parametric Release

The Benefits of Ethylene Oxide Sterilization   (By EOSA)

Since its discovery as an effective sterilant, ethylene oxide (EO) has played a critical role in antimicrobial sterilization that protects public health, and is essential to a functioning and effective U.S. healthcare system. Decades later, it is now used to sterilize more than 20 billion medical devices each year in the U.S. alone. This represents more than 50 percent of all medical devices sterilized annually. EO sterilization is critical in the safe delivery of sterile devices and medical care. The use of EO sterilization provides unparalleled benefits to society by its use throughout the medical community.

Numerous medical, hospital, and laboratory processes rely on EO to sterilize devices and equipment to protect millions of patients from the real risks of infectious diseases caused by bacteria, viruses, and fungi. For the majority of these healthcare products, EO sterilization is the most effective and efficient sterilization technology. The relatively low temperatures at which the EO sterilization occurs provides the medical community significant advantages when sterilizing devices and products. Many critical healthcare products, such as duodenoscopes, are complex and sophisticated devices that are heat and/or moisture-sensitive. The gentle yet thorough nature of EO allows for the sterilization of many critical healthcare products and devices that would otherwise be destroyed and rendered unusable by radiation, moist heat, dry heat, other chemicals, and other alternative sterilization methods. In fact, many of these devices can only be sterilized by EO -- with no practical alternatives currently available.

The use of less effective processing methods can have significant adverse public health consequences. A change in sterilization technology could introduce the real risks of increased morbidity and mortality. In many cases, any change to the sterilization method would require a complete redesign of the product to be sterilized. Even a redesign may not allow the product to be sterilized adequately without the use of EO. Furthermore, it is not feasible for medical device manufacturers to change to alternative sterilization methods within a realistic timeframe. Changes to sterilization technology may cause delays, inadequate sterilization, increased risks to public health, the inability to perform certain medical procedures, and increased healthcare costs. Such modifications have the potential to exchange one risk for another.

The EO sterilization industry is committed to worker safety and closely monitors this issue. Workplace efficacy and safety practices continuously improve as EO sterilization equipment and processes advance with the introduction of advanced technology. In addition, sterilization processes are designed to provide a safe working environment. Many of these modern practices, designed for worker safety, have been approved by the U.S. Food and Drug Administration (FDA) for use in the health care industry. The Association for the Advancement of Medical Instrumentation (AAMI) and the American National Standards Institute (ANSI) have developed consensus-based standards, which are recognized by FDA. By following these standards, hospitals and other facilities are well equipped to ensure the safe and effective use of EO sterilization in healthcare facilities and to minimize any EO exposure to both workers and patients.



Ethylene Oxide, the most widely used gaseous sterilization agent in the world, is applicable to a wide variety of materials including medical devices, medical supplies, drugs, medicine, food, ingredients of food and dentifrices. The use of EO has been developed as a flexible, robust sterilization methodology. EO sterilization is highly effective at relatively low temperatures.

EO has been primarily used as a terminal sterilant for medical devices. The broad application to a range of medical devices is attributed to the fact that EO is compatible with many materials that cannot tolerate or are degraded by radiation and moist heat sterilization. The expanded application for EO sterilization is also due to market and device preferences.

The EO sterilization typically consists of three phases: Preconditioning, Sterilization and Aeration.

Preconditioning: The sterilization load is held in controlled and validated conditions of temperature and relative humidity to heat the product to the sterilization temperature (100-130 degrees Fahrenheit), 40-80% relative humidity for 12-24 hours depending on the cycle.

Sterilization: The sterilization load is transferred to a sterilization chamber, with a water-heated jacket and serves to provide vacuum, steam, nitrogen, gaseous EO and air. The sterilizer process control system runs a sterilization cycle, which is custom-designed and validated for the particular product type with process temperature of typically 100-140 degrees Fahrenheit for 8-16 hours. The sterilant used is 100% Ethylene Oxyde.

Aeration: The sterilizastion load is held under constant temperature to allow desorption of EO and its by-products in controlled and validated conditions (100-130 degrees Fahrenheit) normally between 24 to 48 hours or more.



MSC offers fully customizable sterilization process which give us the ability to sterilize a wide range of medical devices. In order to ensure the correct level of Sterility Assurance is met for a particular product the process has to be validated. The requirements for sterilization process validations are recorded in ANSI/AAMI/ISO 11135:2014, Sterilization of healthcare products - Ethylene Oxide - Requirements for development, validation, and routine control of a sterilization process for medical devices. MSC has validation and quality assurance teams to assist with the steps of a process validation.


The purpose of the validation process is to ensure the sterilization process can be performed and repeated effectively. The validation demostrates the specified level of sterility can be achieved during routine processing. Along with sterility assurance the validation process will demostrate that any remaining residual levels on the product are within acceptable tolerances.

The validation process typically includes the following steps:

- Collecting and reviewing Installation Qualification Data
- Collecting and reviewing Operational Qualification Data
- Collecting and reviewing Performance Qualification Data


Prior to performing validation cycles the following items must be performed:

- Selecting an Appropriate Process Challenge Device: Prior to the validation process a process challenge device must be selected. These devices simulate and evaluate the effectiveness of the sterilization cycle process parameters. A process challenge device (PCD) is a device used to simulate resistance to the sterilization process and used to evaluate the process effectiveness. There are two types of process challenge devices: Internal process challenge and external process challenge devices. Internal process challenge devices are used during cycle validations and external process challenge devices are used during routine processing runs.

- Writing a Protocol: A Validation Protocol outlines all of the validation activities listed in ANSI/AAMI/ISO11135:2014 and ensures all aspects of the validation process are met. If necessary Midwest Sterilization Corporation can recommend a sterilization consultant to assist you with writing a protocol.

-Designing a Representative Load: During the validation a representative product load is assembled. This load can be made of simulated product (Dunnage), sealable product, or a combination of simulated/sealable product.

Validation Testing

Once a protocol has been written and test product has been sent to Midwest Sterilization Corporation the validation test cycle can begin. The Half Cycle Method is typically used during most validation testing and consists of One Fractional Cycle, Three Half Cycle and Three Full Cycles as listed in ANSI/AAMI/ISO11135:2014.

- Fractional Cycle: Is used to demostrate that the external process challenge devices are more difficult to sterilize than your internal process challenge devices.
- Half Cycles: The three half cycle use 50% of the intended gas dwell time of a full sterilization cycle. This cycle is intended to effectively sterilize the product and henceforth show sterility with shortened parameters.
- Full Cycle: The three full cycles measures sterility/product performance and residual level that will occur during routine processing.


Typically, a sterilization process revalidation is to be performed annually as listed in ANSI/AAMI/ISO11135:2014. The level of required revalidation will vary based on product/packaging/process changes and is dependent on customer requirements. A shortened validation process may be performed if only minor changes have taken place and must be performed every year for parametric release cycles.