Dear Sirs,
We are the manufacturers of ETO Sterilisers, in fact we are the company to develop ETO Steriliser in India. We have been manufacturing these sterilisers since 1983. Recently we have introduced a special model having chamber size of 12"x12"x54" (depth) for Angiography Catheters so that they can be kept in a straigt fashion without BENDING OR COILING. We use 100 gms Cartridge for Sterilisation the time taken for Sterilisation is 4 hrs. We want to reduce the time to 2.5 hrs. how can we achieve this, can you explain.
Yours
BHAGWAT K.M.

Good day K.M. BHAGWAT,
Sterilization with EtO is dependant on the concentration of EtO, relative humidity, temperature, and time.
The concentration in your special model is by my calculation 100 grams EtO / 50 liter chamber = 2000 mg/liter. Typical applications use 450 - 700 mg EtO/liter, and concentrations greater than 1000 mg EtO/liter do not appreciably decrease exposure times. So increasing the concentration of EtO will not help much as the concentration in your model already exceeds 1000 mg EtO/liter.
The kill rate at 28% relative humidity is ten times greater than at 97% relative humidity Experiments have shown that 9/15 animal viruses susceptible to normal EtO sterilization cycles survived when the humidity is reduced to less than 20%. Relative humidity that is lower than 20% or higher than 65% reduces the effectiveness of EtO as a sterilant. EtO sterilizers typically maintain a relative humidity between 20 - 40%.
The only other variable remaining that can be adjusted to reduce the time element in the exposure period is temperature. Raising the temperature to 60 C (140 F) should reduce the required exposure period in your special model to 1.75 hours for a D6 reduction (i.e. no growth from a routine 1,000,000 bacillus subtilis var. niger biological spore test).
The same principle applies to the aeration period to remove the residual EtO from the catheters after the sterilization period. With all other variables remaining constant, the higher the temperature in the aeration cabinet, the shorter the aeration time required.
I would suggest you visit www.aami.org and purchase for your business a copy of the ANSI/AAMI/ISO standards for EtO sterilizer manufacturers. Complying with these guidelines will make it easier for your design department to create new products. Each individual guideline contains the rational behind the guideline to make it easier to understand the intent, the rational, the why, behind the guideline. These AAMI guidelines are peer-reviewed with comments solicited from all interested parties so they contain the recent consensus opinion on the best practices/state of the art. Many official governmental organizations around the world base their standards on these standards.
Wishing you success with your endeavors, Pete Bobb