How does Andersen’s Ethylene Oxide – Flexible Chamber Technology (EO-FCT) sterilization process work?

This cut-away of an Andersen sterilizer reveals a loaded sterilization bag — the “Flexible Chamber” — secured with a blue strap around the purge probe.

The sterilization cycle begins by purging excess air from the flexible chamber.

Air molecules, represented by the blue dots, are exhausted from the sterilization bag through the purge probe and purge tube.

With excess air removed, the ethylene oxide (EO or EtO) concentration in the sterilization bag is maximized during sterilization, thereby minimizing the amount of EO needed for effective sterilization.

Once the initial purge is complete, the gas cartridge is manually activated by pressing the button on the cartridge through the wall of the sterilization bag.

Ethylene oxide, represented by the purple dots, spreads throughout the sterilization bag and permeates the items being processed. The gas-impermeable flexible chamber maintains a high gas concentration during the sterilization cycle.

At the end of the sterilization cycle, ventilation of the sterilization bag begins.  A valve in the purge probe opens allowing fresh air, represented by the blue dots, to travel down the probe and into the back of the bag. Ethylene oxide, represented by the purple dots, is exhausted through the purge probe. 

Aeration continues after ventilation, flushing air through the sterilization bag and out the purge tube.  Aeration of the devices in the sterilization bag ends when the operator exits the cycle to remove the sterilization bag from the sterilizer.