How to monitor a steam autoclave: physical, chemical and biological checks
Monitoring tells you whether a cycle actually reached the conditions needed to sterilize. The CDC guideline describes three kinds of checks that work together. Use the schedule builder for a starting plan.
1. Physical monitoring
The sterilizer's display or printout records time, temperature and pressure for each cycle. Read it after every load. A cycle that did not reach its settings is a failed cycle, even if the packs look fine.
2. Chemical indicators
Indicators on the outside of packages show that a package went through a cycle. Indicators inside packages show that steam reached the inside. If an internal or external indicator suggests a problem, the CDC guideline says the item should not be used.
3. Air-removal (Bowie-Dick) test
For prevacuum sterilizers, the guideline calls for an air-removal test in an empty chamber each day the sterilizer is used. Trapped air blocks steam, and this test is designed to show it.
4. Biological indicators
Spore tests are the closest to a direct check that the process kills microorganisms. The guideline says steam sterilizers should be monitored with biological indicators at least weekly, and daily testing helps when a sterilizer runs several loads a day. Each load with implantable items should include a biological indicator, and where feasible implants should be held until the result is negative.
After installation or repair
When a sterilizer is installed, moved, repaired or has failed, it is tested with biological and chemical indicators before routine use. For prevacuum units, three consecutive empty cycles are also run with a Bowie-Dick test.
When a result fails
- Stop using the sterilizer and quarantine the load.
- Check the cycle record, the loading and the packaging for an obvious cause.
- Follow your facility's procedure for retesting and for recalling items from earlier loads.
- Call the manufacturer or service provider if the cause is not clear.