Measurement of Ethylene Oxide Gas and Calculation of a Safe Period for Contact at the Medical Sterilization Unit in Siriraj Hospital

The objectives in measuring the ethylene oxide (EtO) level at the Medical Sterilization Unit in Siriraj Hospital by using a simple Piston gas hand pump, are to examine the residual EtO level at the back of the sterilizer after the sterilizer opened (the end of the sterilization process) at different time periods and to calculate a safe period of time to wait before transferring equipment and supplies to the aerator. The EtO levels at 5,10,15 and 20 minutes after the sterilizer opened were1.5,1.2, 0.7 and 0.4 ppm, respectively. By using a semi-logarithm equation to calculate the slope of elimination between 2 points, the expected time for the concentration of EtO level to be equal to or less than 0.5 ppm would be 18.75 minutes for a room volume of 115.83 cubic meters. A concentration of residual EtO level at 0.5 ppm or lower was safe for workers in routine work environments and could be applied by other laboratories