bowie dick test

Common Causes for Failure of a Bowie-Dick Test

The Bowie-Dick Test is a standard operational test by which hospitals and laboratories can demonstrate proper air removal from their pre-vacuum autoclave chamber. It is primarily useful for testing pre-vacuum cycles that are sterilizing wrapped goods or packs. As we’ve mentioned in previous blog posts, pockets of cool air act as a barrier that prevents steam penetration into these packs, thus inhibiting sterilization.

How To Run a Bowie-Dick Test

Running a Bowie-Dick Test requires placing a small, disposable test pack into the autoclave and running a four-minute sterilization cycle, typically a Bowie-Dick Cycle. The test pack is placed in an empty chamber on the lowest shelf above the drain and the Bowie-Dick Cycle is initiated. The sterilization cycle typically consists of three to four prevacuum pulses, each of which involve injecting steam into the autoclave and then pulling out the air and steam through a vacuum, before reaching the set point of 270°F (or 132°C). For more information on how to run a cycle, see our previous blog post.

Bruce Gillingham, resident autoclave expert of Consolidated Sterilizer Systems, believes it is an imperative process that should be performed each and every day within a hospital setting. This is because many hospitals (and labs) end up shutting down their autoclave at the end of the day, which can lead to unexpected issues when it is turned on again the next day.

“We recommend running a routine 5-minute sterilization cycle at the start of every day. After this is completed run the Bowie-Dick Test Cycle,” said Gillingham. “The initial 5-minute cycle helps to get rid of any air pockets that might be in the jacket. Once this is complete, we recommend running a Bowie-Dick Test before you sterilize your first load of the day.”

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Interpreting the Test Results

“It’s the color change that tells you the steam is penetrating the test pack and pulling all the air out of the autoclave,” according to Gillingham.

A successful Bowie-Dick Test is very evident based on the color change of the thermochormatic paper within the test pack. If the thermochromatic paper turns completely black, then the steam has penetrated the load and the autoclave is operating correctly.

Lack of or a partial color change indicates an unsuccessful Bowie-Dick Test cycle. “If the color hasn’t completely changed, it means something hasn’t worked correctly,” said Gillingham.

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Common Causes for Failure of a Bowie-Dick Test

Cause of Failure Description Possible Solution
Air Leak If air is able to leak into the autoclave chamber, the steam will be unable to penetrate the load to the point of total sterilization. Run a Vacuum Leak Test to further determine if an air leak exists or not.
Unwanted Condensation Occasionally condensation will get trapped in the jacket of the autoclave, which can lead to cold spots at the base of the autoclave.   This could also indicate a wet-steam issue. Check the steam traps on the autoclave. Check steam quality and wetness.
Faulty Test Pack From time to time, a Bowie-Dick Test pack can be faulty. Check the expiration date and make sure the packs are being stored in the proper environment.
No Warm-Up Cycle A warm-up cycle allows the sterilizer chamber and jacket to reach temperature. Run a 5 minute sterilization cycle prior to running the Bowie-Dick Cycle.
Incorrect Procedures Test packs work under very specific conditions. Test packs should be placed in an empty chamber directly over the drain on the bottom rack or shelf. They are designed for use at 270°-273°F (132°-134°C).


Next Steps after a Bowie-Dick Test

A successful Bowie-Dick Test means you can begin sterilizing loads with a prevacuum cycle. Meanwhile, a failed Bowie-Dick Test means further testing is required. If none of the above solutions (see table) work then both the autoclave and the utilities should be checked. The autoclave should not be used with any confidence until the test is repeated with a passing result.

Please contact us with any inquires or if you would like more information. To learn even more about the Bowie-Dick Test, as well as other sterilization cycles, download our 31-page insider’s guide on how to use the 12 most common steam sterilization cycles.

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