ASP STERRAD 100, Service Manual

Page: 36 / 309

Step Five
At the conclusion of the plasma stage, pressure is reduced in the
chamber from 0.5 Torr to 0.4 Torr through the use of a vacuum pump.
Phase 3 - Sterilization B
This is a repeat of the Sterilization A phase, excluding the final step.
Step One
When the chamber has reached the pressure of 0.4 Torr, or less,
approximately 1800 ml of a 59% nominal solution of hydrogen peroxide
is injected into the sterilization chamber. The injection is accomplished
by injector needles puncturing a hydrogen peroxide-containing ampoule
in a cassette. Each cassette contains enough ampoules for five complete
sterilization cycles. The positioning of the cassette and the injection is
automated and software-monitored to ensure injection takes place. This
step lasts 6 minutes.
Step Two
At the end of the 6 minutes, the chamber is vented to atmospheric
pressure with filtered air and held for 2 minutes (short cycle) or 10
minutes (long cycle). Adding filtered air to the chamber further
compresses the hydrogen peroxide, driving it into the lumens and other
intricate mechanisms found in or on many medical devices.
Step Three
After the chamber has been held at atmospheric pressure for two
minutes, there is a reduction of pressure in the chamber from 760 Torr
(atmospheric pressure ) to 0.5 Torr through the use of a vacuum pump.
Step Four
During the plasma step of the cycle, RF energy applied for two minutes
across the electrodes produces a series of reactions in the low pressure
hydrogen peroxide vapor in the chamber. This leads to the generation
and acceleration of charged particles and the generation of free radicals
and other reactive chemical species. This action enhances
decomposition of hydrogen peroxide which has been added to the
chamber.
System Operation STERRAD 100 S Theory of Operation
2-20 STERRAD® 100 Sterilizer ASP Service Guide rev. D