Bowie-Dick, Biological & Leak Tests in Steam Sterilization

Steam sterilizers need constant evaluation to ensure adequate performance air removal is achieved, and proper sterilization parameters are satisfied. If air is not properly removed by the vacuum, cool air will act as a barrier which prevents steam from penetrating the load (wrapped instruments). If sterilization parameters are not being met, microorganisms could contaminate the load. Leak tests can provide a service technician with advanced warnings of potential problems within the system. All three tests are important to provide the appropriate confidence level in the sterilization of the processed load.

Importance of Running a Warm-Up Cycle

When sterilizers have been shut down, turned off overnight, or have been idle, a warm-up cycle is recommended before running diagnostics tests. Cold components can contribute to a failed diagnostic test. Running a warm-up cycle can help avoid retesting, downtime, or unnecessary maintenance calls.

Bowie-Dick Test

One of the most common standard operational tests performed, is the Bowie-Dick test. You may be wondering, what is a Bowie-Dick test? The Bowie Dick test is a diagnostic test specifically designed for prevac steam sterilizers. The test gives a visual of the sterilizer’s vacuum system and determines if it is effectively removing the air that has been trapped in or leaked into the sterilization chamber.

The Bowie-Dick disposable test-pack should be placed into the empty chamber, on the lowest shelf, directly above the drain. The steam sterilization cycle should then run for 3½ – 4 minutes, at a temperature of 270 – 273 degrees F. Most current sterilizers have a specific Bowie-Dick cycle pre-programmed. Make sure that the disposable test-pack is the only item in the chamber during the diagnostics test. If you have questions about Bowie-Dick test troubleshooting, contact our team.

What is a Bowie-Dick Test Pack?

A Bowie-Dick disposable test-pack consists of thermochromatic (temperature sensitive) paper, pressed between porous substrates and reticulated foam. The color-change pattern on the sheets can determine whether the steam has penetrated the porous load. A uniform color-change pattern indicates the test has passed and that steam has penetrated throughout the entire test-pack. A non-uniform color-change indicates a failed test and can be indicative of an insufficient vacuum or inadequate steam temperature.

Biological Indicators

A biological indicator (BI) is a device used to routinely monitor and qualify adequate conditions were met within the sterilization chamber to achieve microbial inactivation. This is especially important for viable microorganisms that are particularly resistance to the sterilization process. This device is generally placed on the bottom shelf near the drain and once the cycle is complete the BI is then incubated to determine if any spores survived the sterilization process which will ultimately provide a final pass or final fail result for this biological test.

According to AAMI ST79:20172, biological indicators should be monitored weekly but more preferably on a daily basis.

Vacuum Leak Rate Test

While not a test of sterilization efficacy, the Leak Rate Test can be a good diagnostic tool to let an operator or technician know how well the system is functioning. This test measures how much vacuum depth is lost when the plumbing and components are exposed to vacuum conditions. A perfectly sealed chamber will have no leaks or a threshold of up to 1.0 mm Hg per minute over a specified amount of time. As regular leak rate tests are part of a comprehensive preventive maintenance program, many facilities do not include them as a part of their standard daily or weekly testing regimen. Check your departments SOP to ensure whether or not you are required to run this test as an operator, on what schedule, and how to perform a leak rate test or how to get a pressure test leak rate. It is important to note that a high leak rate is NOT an indication of a sterilization problem. As long as your Bowie-Dick and Biological indicator tests are passing, your sterilization process is effective. A high leak rate is only an indication of potential maintenance needs. The vacuum leak rate test is just one of the leak testing methods we use to ensure proper operation of highly specialized equipment. If you have questions surrounding how often do you run a leak test for sterilization, contact our specialists for help.

Why We Need These Tests?

The three diagnostic tests mentioned above play a complimentary role in qualifying that sterilization of processed goods or loads has been adequately met and that the sterilizer is functioning correctly. Check your facilities SOP to ensure that the tests are being performed correctly and on schedule and that the results are recorded accurately.

At ERD, we understand that the Sterile Processing Department is the heart of everything that happens in your facility. As the first line of defense against infection the efficacy, reliability and precision functioning of your processing equipment is of utmost importance. Let our factory trained technicians help you ensure that the equipment you use every day exceeds all expectations for patient safety.

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