Information
editThis will be a page contiaing information about sterilization using Ethylene Oxide or EtO.
--Scott H. (talk) 16:27, 5 January 2009 (UTC)
Ethylene Oxide (EtO) is used for sterilizing many different types of products like medical instruments and spices. A sterilizer can be as small as a microwave oven or as large as a 18 wheel truck trailer. There are many sterilization plants around the world with various capcities.
The process is fairly simple. In a sterilizer plant it starts with a pre-conditioning period in a temperature and humidity controled room where any bacteria is given good conditions to grow. After that time the product is placed in a sterilization vacume chamber where EtO is drawn in under negative pressure and used to kill the bacteria. Numerous gas washes are used to ensure the EtO completely penetrates the product containers. Nitrogen and air washes are used afterward to remove the EtO from the product. After this, the product is moved to a degasing room to air the product out further before it is shipped back to the customer.
The used EtO is converted Ethylene Gycol (antifreeze) after the process is complete. Any addtional EtO released in the degasing rooms is absorbed in a "safe cell" containging a material that absorbes EtO. The end result is very little or no EtO released to the enviroment. Some plants will burn the used EtO but this can be dangerous and does not create the Ethylene Glycol that can be use in other processes.
The control of the process is a bit more complex. The entire process is computer controled using air acutated controls on the chambers to ensure no electric sparks could ignite the EtO. PLC's (Programable Logic Contolers) are used for safety and process monitoring. All process data is collected in a database and reports are generated for analysis of each load sterilized. EtO, temperature and humidity levels are monitored through sensors in the chambers and through passive data recording devices attached to the products being sterilized. The data recorders are collected and read after the process completes and the chamber sensors are monitored in real time.
For quality control a customer will use a biologic indicator or a parametric release process to ensure a complete kill. A biologic indicator unit contains a bacteria that is hard to kill. The indicator is designed to test the ability of the EtO process to penetrate and kill the bacteria it contains. The indicators are placed on the target product in such a way as to fully test and ensure the EtO has competetly penetrated the product being sterilized. If the EtO has completely penetrated and killed the indicator bacteria then the product can be considered sterile. The parametric release process starts with a biologic indicator on the load and the process paramenters are closely monitor and recorded. Once a consitent kill is obtained using the designed process cycle, the biologic indicators are no longer used and the process report is used as proof of sterilization.
Various calculations are used in the processing, storage and use of EtO for sterilization...