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Bowie-Dick Tests and Troubleshooting Guide

What is a Bowie-Dick Test?

Bowie-Dick testBowie-Dick (Air-Removal) tests evaluate the performance of prevacuum sterilizers by confirming adequate air removal from the sterilizer chamber. These air removal tests have been improved over the years, but you may be wondering, are Bowie-Dick tests still relevant in sterilizers that have programmed leak tests?

To fully answer why this test is still important today, we must first understand why it is important to remove air from the sterilizer. Air within a steam sterilizer is often referred to as a non-condensable gas (NCG). As the name indicates, non-condensable gases do not condense when touching a colder item. These gases act like a shield between the steam and the item, potentially shielding bacteria and preventing proper sterilization.

Even today’s sterilizers are not capable of detecting NCG because it could be hiding anywhere in the chamber. Sensors would need to be placed within the packs exactly where the NCG would either be trapped or collected in order to detect it. This is not possible and supports why air-removal tests are still very relevant to today’s modern sterilizers for autoclave testing. The Vacuum Leak Test programmed on your autoclaved only measures the integrity of the sealed pressure vessel and associated piping to assure air is not being admitted to the sterilizer during the vacuum draw downs.

In addition to air-removal, modern Bowie-Dick Tests such as the VERIFY® Bowie-Dick Test Pack provide a critical control for sterilizer performance and verification of steam quality. It ensures the sterilizer can provide the validated preconditioning required, and aid in detection of steam quality that could interfere with sterilization of complex instrumentation.

Interested in Earning Continuing Education (CE) Credit?

Earn 1.0 CE Hours by learning about Bowie-Dick tests and the key considerations when selecting a Bowie-Dick test for your facility.

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How to Run a Bowie-Dick Test

Bowie-Dick test pack Recommended use of a Bowie-Dick Test is outlined in the Association for the Advancement of Medical Instrumentation's (AAMI)  guidance ANSI/AAMI ST79 Comprehensive Guide to steam sterilization and sterility assurance in health care facilities. Bowie-Dick Tests are used to qualify sterilizer performance when first installed, anytime it is moved, and following a major repair. This is qualification testing and requires three consecutive test cycles with passing results. Bowie-Dick Tests are also used each day the sterilizer is in operation, and only one passing test cycle is required for routine monitoring.

The Bowie-Dick Test procedure is the same for both qualification and routine testing.

Step 1: Perform a warm-up cycle. This is a critical step needed to properly heat up the sterilizer and can result in false failed Bowie-Dick Test results when not performed. It is the most common step missed, resulting in unnecessary downtime.

Bowie-Dick test pack in sterilizer Step 2: Place the test pack. A Bowie-Dick Test pack must be placed on the bottom rack of the sterilizer, or sterilizer cart, directly over the chamber drain. The drain is where the vacuum is drawn, and any residual air in the chamber will naturally migrate to the test pack.

Step 3: Ensure the chamber is empty. Only the sterilizer cart (on medium and floor loader sterilizers) should be present for a proper test. If the cart is not included, the result could be superheated steam and a failed test.

Step 4: Run the cycle. ANSI/AAMI ST79 does not provide specific guidance on cycle parameters for the test. However, it does indicate that the programmed exposure time should be between 3.5 and 4 minutes. Always follow the sterilizer and Bowie-Dick Test pack's instructions for use on cycle parameters for testing.

Tip – The top sources of a failed Bowie-Dick Test are:
1. Door Gasket/Air Leak
2. Steam Supply Issues
3. Steam Trap or Safety Valve Failures

Step 5: Open the test pack and interpret results.

Interpreting a Bowie-Dick Test pack varies by manufacturer and can show you more than just air leaks. It can also provide information including moisture presence, steam quality issues, and the presence of NCG in plumbing lines outside of the sterilizer. To assist, STERIS has developed A Bowie-Dick Troubleshooting Guide. Review the Bowie-Dick interpretation guide to better understand what a failed Bowie-Dick Test look like to understand what needs to be done to avoid downtime.

 

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