Failed Autoclave Tests - What to do?

Don't Panic! There only a few ways autoclave testing can FAIL and below you will find the types of failure; their causes and what you can do.

Failed Biological/Spore Test

Biological tests are usually considered the most important test as they best reflect whether biological materials remain on your instruments.

Operator error is the most common reason for a failed spore test. If your autoclave has automatic controls and completing cycles without giving any failure messages, the chances are that the causes of a failed spore test were due to some type of operator error. You may need to review the sterilization procedures your staff has been using to see if you could identify the problem. Firstly you have to make sure that they are not overloading the Autoclave. Check the manufacturer’s specifications in regards to how the sterilizer should be loaded. The next thing you will need to check is the time and temperature settings. It is possible that the factory default settings somehow got changed or the operator is simply not running the sterilizer hot enough or long enough. Manufactures default settings can vary a little but generally an autoclave has to maintain 270F degrees Fahrenheit for 12 minutes. Lastly if the Autoclave uses manual controls, you will need to monitor and record"

Failed Control Test

To ensure that the microorganisms are working it is required that a positive control tube or vial is set aside (a bacterial vial that hasn't been in the autoclave). If the control vial does not go through a color change, that means that the control vial was not viable to begin with.

Reasons that a control could pass, when it should fail is:

  • The spore was not incubated correctly

  • The spore is expired

  • There is a problem with that particular batch of LOT numbers.

Failed Chemical Test

Possible reasons for Chemical Tests failing:

  • Overloading Machine and improper stacking

  • Poorly wrapped casettes

  • Autoclave malfunction

In the event of a failed chemical test run the autoclave again without any equipment in the machine. If the test passing failure was possibly due to overloading machine. If the test fails a second time. Take the machine out of circulation and get it serviced. Any equipment that was part of the failed load will have to be sterilized again before use.

Failed Washer/Disinfectant Tests

There are many things that can affect the quality of your cleaning protocol. Rather than assuming that your instruments are clean just by looking at them, let’s consider some of the common process failures for your Washer-Disinfector:

  • Incorrect positioning of Washer-Disinfector Monitor i.e. positioning some of the instruments in the load

  • prevents direct access of cleaning solutions to the Cleaning Monitor (shadowing)

  • Overloading or incorrect loading

  • Cleaning time too short

  • Cleaning temperature does not match recommendation for solutions

  • Dosage of the cleaning solutions too low

  • No uniform distribution of detergent

  • Clogged or loose spray arms

  • Insufficient water pressure

  • Residuals from pre-cleaning

  • Incorrect temperature for solutions

  • No cold pre-rinsing step in place or pre-rinsing too hot

  • Complete breakdown of the washing machine or the detergent

Failed Ultrasonic Tests

The Ultrasonic test has a few different versions - the most common is the foil test. There are other options such as the Cleaning Monitor strip with holders - patches that have patterns or liquids that change colour.

There are many things that can affect the quality of your cleaning protocol. Here are some of the common process failures for your Ultrasonic machine:
* Ineffective cavitation
* Overloading
* Insufficient time, temperature and/or detergent


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