What is sterilization?

Sterilization is the removal of all life forms and agents from the surface of a material or from a fluid or compound.

Examples of such agents include:

  • Bacteria
  • Fungi
  • Viruses
  • Spores

Proper cleaning is a very important step for certain businesses that require sterilization on a regular basis. A sterilization process helps kill bacteria to ensure the instruments and devices workers use, such as medical devices, are safe for use or do not contaminate other products, materials, or individuals.

Industries that rely on this the most are:

  • Food and beverage industry
  • Pharmaceutical industry
  • Medical industry

Not only does proper cleaning keep products safe for people, but it may allow for some products to be used again. Safety and cost benefits are common reasons sterilization methods are used.

There are many ways a material can be cleaned. For example, some metal objects can be cleaned with acids. However, for some products, this is simply too harsh and may ruin them. Instead, gamma and ethylene oxide sterilization are two of the most common options to choose from.

So how do they compare? Below you will find out more about both options and what they mean for business.

Questions we will answer include:

  • How do they work?
  • Which materials work best with each process?
  • What are the pros and cons?

With this information, you can better determine:

  • Which process is right for your product
  • Why one process may be better than the others
  • How the pros and cons impact the end result

Ethylene Oxide Gas Sterilization

Commonly known as Gas Sterilization, EO (EO) sterilization is performed by exposing the material(s) to the toxic and volatile ethylene oxide gas. This method is also often called ETO sterilization. This process is done in a heavily controlled area and within a specific amount of time.

In its pure form, ethylene oxide gas is flammable and explosive if it comes in contact with air. As a result, it is usually weakened with inactive gases. Not only does this lessen its toxicity, but also makes it easier and safer to handle.

The process

Step one:

The material needs to be prepared before disinfection. This is done in a room that meets the following:

  • Made to heat and humidify the product to a stable temperature
  • Moisture content before it is placed in the chamber

The cleaning process takes place in a vacuum-tight chamber and when all the air in the chamber is removed, a set amount of EO ensures proper cleansing is achieved.

Step two:

The next step is to add the material that is to be cleaned. During the ongoing process, the following is closely monitored:

  • Time of exposure
  • Temperature
  • EO gas concentration levels
  • The humidity of the gas

Step three:

Sometimes during the process, the material is softened. To avoid more damage, the product is washed several times at a controlled pressure.

Additional Information

EO sterilization is used mostly:

  • In hospitals to sterilize medical devices
  • For plastics
  • For other heat-sensitive materials

It is not ideal for materials that absorb gases. Such materials are likely to leach ethylene oxide into future processes, which will ruin the product as a result.


  • A wide range of materials can be cleaned using this process.
  • Already packed materials can be cleaned using the process because EO can go through cartons and sealed film


  • Ethylene oxide may be harmful to people.
  • The process requires the need for more control.
  • EO is highly flammable. When air is present, it can create its own oxygen.
  • Possible change in smell or color of the materials.

Gamma Irradiation Sterilization

Gamma sterilization, also known as gamma irradiation sterilization, requires a radiation source and is done by exposing a material to a controlled dose of gamma rays (radiation dose). The radiation breaks the bond in the microorganisms’ DNA ultimately killing it while also preventing further reproduction. The radiation source used is cobalt 60 and this material is often used for applications such as sterilization, decontamination, or to modify materials.

One of the key benefits of using gamma irradiation is that it has a high penetration ability, allowing workers to target a radiation dose to particular areas of products that may be highly dense. This process is effective for sterilizing products with varying densities. Better yet, it can penetrate products that are sealed in their final packaging to ensure the complete sterility of the packaging and raw materials.

The Gamma Radiation Sterilization Process

Single-step process:

Materials cleaned using gamma rays do not need to be prepared and can be put together and packaged before the process. The radiation is applied in a safe and controlled environment. Be aware that a single dose of radiation may take between a couple of minutes to a few hours to clean a product. It depends on the thickness or volume of the material.

Gamma radiation is best for:

  • Acetyls (low doses of radiation)
  • Polycarbonates
  • Acrylics
  • PVDF
  • Objects with a high density

It is commonly used at:

  • Industrial Plants
  • Pharmaceutical Companies


  • Gamma is the ideal choice for materials that are stored for a long period of time
  • The process does not create heat or moisture
  • Less expensive
  • Cleaner
  • After the cleansing process, there is no trace of radioactivity


  • Some materials may be a slightly different color after the process.

Note: Some plastics perform better after the process is complete— this instance falls under the product modification category mentioned above.

ISO 11137: Sterilization for Medical Devices

Medical devices can be sterilized in numerous ways including but not limited to:

  • Ethylene Oxide Gas (EO sterilization)
  • Gamma radiation
  • Steam processing (moist heat/ steam)
  • Dry heat
  • Vaporized Hydrogen Peroxide
  • Chlorine Dioxide gas
  • Nitrogen Dioxide

Healthcare devices and ISO 11137

Medical devices fall under ISO 11137, which outlines the specific requirements throughout the sterilization process in order for a device to be considered sterile. This regulation can be broken down into two parts.

Part one: ISO 11137-1:2006

This aspect focuses on the obligations for "development, validation, and routine control of a sterilization process for medical devices."

Part two: ISO 11137-2:2006

This part of the regulation is focused on establishing the sterilization dose used to ensure a sterile product.

The process must be performed routinely and controlled, products require sterilization validation, and this regulation also takes into account the products' environment, worker hygiene, packaging methods, storage methods, sterilization doses, and more. According to the FDA, about 50% of all sterile medical devices in the United States are sterilized using ethylene oxide.

Examples of items that use ethylene oxide sterilization for medical devices include wound dressings for general health care, to stents that are more specialized for specific parts of the body. In some cases, EO may be the only suitable method that sterilizes a device without causing damage throughout the process-- devices are often made from polymers such as plastic or resin, as well as metals or glass.

Devices may also have multiple layers of packaging and areas that are hard to reach. A catheter is an example of a device that has areas that are hard to reach and commonly relies on EO sterilization.

Which Option is the Best?

Choosing between EO sterilization or Gamma depends on the type of product being cleaned. However, it is understood that Gamma and EO typically meet the requirements of packaged laboratory products. EO sterilization is a popular choice simply because it tends to be the most versatile since it can be used on plastics and other heat-sensitive products. However, it may have more of a risk with its use.

To ensure that you’re using the best cleaning process, you should examine the following:

  • Type of material
  • Heat-resistance level
  • How workers perform the process
  • The possible need for a validated sterilization process (93/42/EEC)
  • Microbial controls before sterilization and sterilization testing after to confirm the effectiveness
  • An understanding of product families and categories that may allow different devices to be sterilized together
  • The requirements for establishing the minimum dose of radiation or EO gas
  • How to monitor and control sterilization that is outsourced to a third-party organization
  • A well-documented process for auditors or "Notified Bodies"
  • Cost

You’ll also want to weigh if the cons of either method could influence how the product is used in the future or how it will impact the workers who use it.


International Enviroguard, offers Gamma Radiated products and other protection solutions that help your workers remain:

  • Clean
  • Safe from toxic acids, bases, and caustics
  • Radiation-free
  • and better prevent cross-contamination

Keep in mind, both processes outlined above require a sterile environment where they can be carried out risk- and contamination-free. Don’t hesitate to reach out to our team if you have questions about our sterile garments.