Hello to all

I run a sterilising department in New Zealand and am doing some research into ETO aeration times. The AORN Journal, August 1999 printed some information on their recommended practices relating to the ETO sterilisation process. What I would like information on is how long other hospitals aerate for, how these times were decided on and whether information is provided by manufacturers on recommended aeration times for products? To date I have not been able to get a recommended length of aeration time when I have asked a provider of product even though their information recommends ETO sterilisation. Look forward to your comments.

Alison Stewart
Sterile Production Centre, Wellington Hospital, New Zealand

I would also love some info on ETO aeration times. Did you find any information? Could you please forward on to me if you did. My email is . I have been looking everywhere for some information on aeration times. I remember from my old hospital that everything had to be aerated at least 8 hours but now where I work they say things have different times even tho no one has a list of the times... Any help you can give me would be appreciated. Thank you.
Geneva in Ohio

EO Residual Limits

EO sterilization in today's hospitals became a complicated process. Up to now the standard recommendation was: EO residuals and its primary by-products, ethylene chlorhydrin (ECH) and ethylene glycol (EG) are reduced to a safe level by the standard mechanical aeration time for 12 hours at 50°C. Due to the growing multitude of thermo labile devices, it is not that simple anymore. The safe aeration time is dependent upon many factors including; Composition, thickness, design configuration and weight of the device and wrapping material, and the intended use of the device (external or implant able) which influences the permissible limit of residual ethylene oxide. Some devices require a significantly longer aeration time than the minimum recommendations mentions above.

In these cases it is a must and the responsibility of the manufacturer to provide complete instructions for sterilization and aeration.

In the European standard EN ISO 10993-7 the permissible concentration for EO and its by-products in a sterile item are recommended in accordance with the intended duration of patient exposure. For short-term use, for less than 24 h the average dose released to a patient should not exceed 20 mg. In case of continued contact involving single or multiple use of the sterile item for 30 days or more, the average daily dose is 0.1 mg EO per day, with no more than 60 mg monthly and nor more than 2500 mg during the patient's lifetime. This means the risk to the patient is no longer depended to the magnitude of the actual amount of residual EO and by-product sorption. It is defined by the concentration released under use conditions.

Other International EO Residual Limits are:

• French Pharmacopoeia
  EO: maximum of 2 ppm
• German Health Agency
  EO: no residues detectable, method used must be validated and have sensitivity of at least 1 ppm
• Italian Pharmacopoeia
  EO: 2 ppm for products weighing < 200g; 250 mg/product for products weighing > 100 g

Keep in mind: to sterilize in EO only what can't be sterilized in steam.

A good Website to the issue EO is: www.devicelink.com

As Josy Holdener said, the aeration time depends on the product. But the aeration process is also important. Some factors playing a role are temperature, atmosphere change rates and, if applicable, depth of pressure pulses (active aeration). Reducing the aeration period can be achieved by changing one or more of these parameters. In the Netherlands, where EO sterilisation is no longer performed in hospitals but in sterilisation companies, aeration periods can be as long as 7 days!!

Kind regards,

Arjan van Drongelen
Dutch National Institute for public Health and the Environment (RIVM)

Any opinions expressed in the e-mail are those of the individual and not necessarily the RIVM.