The best way to ensure that an autoclave is performing properly is to conduct routine maintenance. Follow the manufacturer’s recommendations for routine preventative maintenance and cleaning the chamber. Record all maintenance activities in the appropriate log.
In absence of manufacturer guidelines, the following cleaning procedure may be used:
- Wash wetted portion of the chamber thoroughly using a mild diluted detergent and a soft cloth or pad. A nylon soap pad may be used for surface film not easily removed. Never use a wire brush, abrasives, or steel wool on door and chamber assembly.
- Ensure drains or screens on the floor of the autoclave are not blocked with debris.
- After washing, thoroughly rinse with clean, soft water.
The purpose of efficacy testing is to ensure the inactivation of biological materials by autoclaving. The BMBL (Biosafety in Microbiological and Biomedical Laboratories) recommends routine efficacy monitoring via the use of biological indicators. In addition, the CDC’s disinfection guidance recommends weekly inclusion of biological indicators along with inclusion of chemical indicators in every load. Perform efficacy testing monthly, at a minimum, using biological indicators. An autoclave printout has a positive value as a general day-to-day log of usage and cycle settings but provides no evidence of the inactivation of biologicals or steam penetration through the innermost parts of a load. Annual manufacturer’s maintenance checks of the devices would be inadequate to ensure sterilization efficacy of a frequently used autoclave.
Regular testing by use of a sterility indicator serves to verify that:
- Sufficient temperature was reached to kill microorganisms.
- The duration of the cycle was sufficient to kill microorganisms.
- Adequate steam penetration occurred throughout a load to kill microorganisms.
- Efficacy test results must be recorded, retained, and available to all parties using the autoclave.
Efficacy testing must be described in the Disinfection/Inactivation section of your Biosafety Protocol. Laboratory personnel must follow efficacy testing procedures described in their approved Biosafety Protocol. There are several different types of indicators that can be used to verify proper autoclave operation. Use indicators according to manufacturer/supplier instructions. Supplies can be found on ShopUW+ from vendors such as Mesa Labs, Steris, 3M Attest, Croxxtex, and Propper Manufacturing.
Embedding Indicators: These examples demonstrate how to use biological or chemical indicators when autoclaving. A. Place a biological or chemical indicator in a conical tube. Attach the tube to an autoclavable string and place the conical tube inside of the bag of waste. Loosely tie the string around the outside of the bag so the indicator can be retrieved and read after the cycle has completed. B. Place a biological or chemical indicator inside a conical tube. Using autoclave safe tape, secure the tube to one end of a long wooden dowel rod. Place the dowel rod, indicator side down, into the middle of the bag of waste, and loosely close the bag opening around the dowel rod using autoclave tape.
Efficacy Testing Failure:
Autoclave failure is usually due to operator/user error or mechanical failure. Examples include:
- Containers blocking access of steam to the load
- Improperly venting bags or containers prior to autoclaving
- Not adding water to a dry load before autoclaving
- Autoclaving a bag of waste that is too large for the autoclave
- Over-filling a biohazard bag
If efficacy test results indicate that the autoclave failed, first check the autoclave log to ensure the correct temperature and cycle time were used. If not, adjust settings to the correct time/temperature and rerun the load with new indicators.
- If the correct time and temperature were achieved during the efficacy test, and the autoclave did not pass, change one or more of the following parameters and rerun the load with a new indicator.
- Density: Load the bag 2/3 of the holding capacity or less. Do not compress the waste to fit more in the bag. Steam cannot penetrate completely through densely packed waste bags.
- Loading: Change how materials are loaded into the autoclave to allow steam to better move from the top of the chamber to the bottom and penetrate the load:
- Avoid crowding or stacking.
- Make sure bags are not touching the top or sides of the autoclave.
- Try using shallower trays; make sure they will still contain any spills.
- Steam: Add approximately 250ml of water to dry waste loads to facilitate steam generation.
- Time: Increase the cycle time by 15 minutes. If the cycle fails again, try adjusting another parameter. Cycle time may be increased by 15-minute increments until the cycle passes; however, this indicates that cycle times will need to be longer for each regular load run.
- Record the parameters changed for the re-test on the autoclave record/log.
- The changes will become the new parameters for autoclaving waste in this specific autoclave, so be sure to make whatever changes are necessary to protocols and instructions for autoclave use; inform others who use the autoclave.
- If changing parameters is ineffective, call the appropriate autoclave service provider as indicated in the manufacturer’s manual or laboratory records. Mechanical failure of the autoclave must be addressed by a trained technician. Contact the service company responsible for maintenance, the department or building manager, or Physical Plant Customer Service.
- Post a sign on the autoclave stating that it is “Not in Use” until maintenance has been performed and the autoclave has been verified to be operating properly via efficacy testing.