EtO-MD Sterilization and Autoclave Sterilization Complement each Other

Steam Autoclave

Steam autoclave is the oldest and safest sterilization method in the medical equipment industry, its only drawback being the harsh conditions it imposes on the items being sterilized, by exposing them to extreme heat, pressure and humidity for 10-60 minutes. The steam reaches 121-148°C (250-300°F) in the pressure chamber at 15 P.S.I. The sterilization period is dependent on the temperature and size of load.

Configurable autoclave cycles allow the user to customize the sterilization cycle for items such as hard items, wrapped items, liquids in vented containers, waste, and glassware. The fastest steam sterilization used is flash sterilization and it can be accomplished using either gravity-displacement, or pre-vacuum cycles. It is generally a high-speed steam sterilization of an unwrapped instrument or device for 3 to 10 minutes in 132°C saturated steam. This type of sterilization is only intended for use in hospital operating rooms for urgently needed equipment.

In the steam autoclave process, microorganisms are killed by heat, and this is accelerated by the addition of moisture. Steam by itself is not sufficient for sterilization, and pressure that is greater than atmospheric is needed to increase the temperature of steam for thermal destruction of microbial life. Steam, for a specified time at required temperature, must penetrate every fiber and reach every surface of items to be sterilized. When steam enters the sterilization chamber under pressure;

• It condenses upon contact with cold items.

• This condensation frees heat, simultaneously heating and wetting all items in the load, thus providing heat and moisture.

Any living thing will be killed when exposed to saturated steam at 120°C (250° F) longer than 15 minutes. As the autoclave's temperature is increased, time may be decreased. A minimum temperature-time relationship must be maintained throughout all portions of load to obtain effective sterilization. At the end of the cycle, re-evaporation of water condensate must effectively dry contents of the load to maintain sterility.


Steam autoclave is used mostly for surgical instruments. This method is not well suited for heat sensitive materials and instruments. Many surgical instruments are not designed to withstand prolonged heat and moisture of the steam sterilization process. This leads to the search of an alternative sterilization method: EtO sterilization.

Ethylene Oxide ( EtO) Gas

Chamber EtO Sterilization

Ethylene Oxide (EtO or EO) gas was introduced in the 1950’s, and it is an effective, low temperature chemical sterilization method. It also takes longer than steam sterilization, typically, 16-18 hours for a complete cycle. Temperatures reached during sterilization are usually in the 50-60°C range. Ethylene oxide ( EtO) is a chemical agent that kills microorganisms, including spores. EtO gas must have direct contact with microorganisms on the items to be sterilized. The aeration time may be long and is needed to make sterilized items safe for handling and patient use.

In general, EtO gas is a reliable and safe agent for sterilization when handled properly. OSHA also has special handling guidelines for Ethylene Oxide.


EtO is used to sterilize items that are heat or moisture sensitive, especially when large loads are possible, in order to benefit from economies of scale. Particlularly suited for semi-industrial applications.

Andersen System: EtO micro-dose sterilization

In order to fill the void between the chamber sterilization and the autoclave sterilization system, Andersen developed in the late 50's the gas-diffusion sterilization method whereby a specially designed bag is used in order to eliminate the need to flood a chamber with EtO. This has the effect of minimizing the use of gas and tremendously reducing the economic and environmental costs associated with the traditional process. This system has been used extensively worldwide among various user groups such as hospitals, veterinarian practices, dental practices and medical device manufacturers.


Due to its handling ease, affordability and tremendous versatility, gas-diffusion technology has emerged as an all-purpose, widely accepted sterilization method especilly suited for expensive medical equipment (endoscopes, electronics, fiber-optics, prosthesis, etc.), disposable items, delicat items (paper, plastics, rubber) that heat would damage, and all sorts of medical devices. For a more complete list of the items that can be sterilized using gas-diffusion sterilization, see the alphabetical product list. Also see Andersen's

EtO vs. Autoclave Comparison Table

Andersen System:
EtO micro-dose sterilization
Traditional EtO chamber sterilization
25 degrees C 50-60 degrees C 121-148 degrees C
Cycle time
3.5 h. up 16 h. up 15 min-up
EtO Gas EtO Gas Steam
Sterilization range
Sterilizes most materials excluding liquids, food or drugs. You can sterilize plastic, paper, electronics, etc. Sterilizes most materials excluding liquids, food or drugs. You can sterilize plastic, paper, electronics, etc. Stainless steel, pyrex, selected rigid materials
Typical practice type
Clinical, hospital, dental, veterinarian, medical device manufacturing Hospital, medical device manufacturing Clinical, hospital, dental
Operator skill level
Average High Low
Environmental impact
None if abated EtO emissions High energy use
System Price range
$3,999-$50,000 $50,000-$150,000 $5,000- $10,000

-Low temperature
-Sterilizer virtually anything
- Can sterilize and package in one step
-Relatively fast
-Minimal gas use

-Large loads
-Low temperature
-Sterilizer virtually anything
-Relatively fast


- Relatively small loads
- Requires special safety handling
- Not suited for liquids, drugs nor foods.

-Long cycles
-Toxic byproduct
-Long aeration
-Gas use
-Requires special safety handling

- Relativel;y small loads
- Wets and heats
-Corrosion is
-Not suited for heat sensitive materials


Excellent as general-purpose sterilizer.
Great for scopes and high-end medical equipment.

Cost-effective sterilization for large loads. Excellent for quick sterilization of metal instruments