CRCST Exam PrepQuick answer: The Bowie-Dick test is the daily air-removal check for dynamic-air-removal (prevacuum) steam sterilizers, run in an empty chamber before the first processed load. Uniform color change on the indicator sheet means pass. A non-uniform or faded color change means fail: do not use the sterilizer until the problem is investigated and a retest passes. A test run wrong (expired pack, wrong sterilizer type, loaded chamber) is invalid and must be repeated correctly.
1What the test is really checking
Prevacuum steam sterilizers work by pulling air out of the chamber and then flooding it with steam. If air removal is incomplete, pockets of trapped air remain, and air is a terrible heat conductor: instruments sitting in those pockets do not reach sterilization temperature even while the gauges look perfect. The Bowie-Dick test exists to catch exactly that failure mode before any patient instruments go through.
The test pack is designed to mimic a dense load, with a chemical indicator sheet at its center, the hardest place for steam to reach. If the air removal system is working, steam penetrates the whole pack evenly and the sheet changes color uniformly. If air is trapped anywhere, that spot stays cooler and the sheet tells the story. Think of it as a daily lie-detector test for the sterilizer's air removal system.
2Running it right (or the result means nothing)
A result is only trustworthy if the test was run correctly. The setup rules the exam expects you to know:
- Daily, before the first processed load. It is the morning gatekeeper. No instrument loads run until the test passes.
- Empty chamber. The test pack goes in alone. Running it on top of an instrument load invalidates the test.
- Bottom shelf, over the drain. That is the hardest spot in the chamber for air removal, so passing there means passing everywhere.
- Prevacuum sterilizers only. The test is designed for dynamic-air-removal machines. Running it on a gravity sterilizer answers a question nobody asked.
- Valid, in-date test pack. Check expiration and pack integrity before running. An expired or damaged pack cannot give a trustworthy result.
- The correct cycle per the pack and sterilizer instructions. Wrong cycle, wrong test.
3Reading the sheet: the three outcomes
Pass: uniform color change
The indicator sheet shows an even, uniform color change across its entire surface. Air was removed, steam penetrated evenly, and the sterilizer is cleared for the day's loads. Document the pass and move on. This is the outcome you want to see every morning.
Fail: non-uniform color change
Any area that is lighter, faded, or unchanged while the rest of the sheet changed color means air was trapped there. Steam did not penetrate evenly, which means instrument loads would have cold spots too. The sterilizer is grounded: no loads until the failure is investigated, corrected, documented, and a retest passes. Common culprits include air leaks, steam quality problems, and drain or vacuum system issues.
Invalid: the test itself was flawed
Sometimes the result cannot be trusted at all: the test pack was expired or damaged, the pack sat in the wrong spot, the chamber was loaded, the wrong cycle ran, or it ran on the wrong sterilizer type. An invalid test is neither a pass nor a fail. It is a do-over: fix the setup and repeat the test correctly. Treating an invalid test as a pass is one of the exam's favorite traps.
4Practice reading results
The exam loves Bowie-Dick scenarios. Work through these four and see if you call each one right:
5What happens after a fail
A failed Bowie-Dick test is a stop-work event, not a shrug. The sequence:
- Do not process loads. The sterilizer is out of service for instruments until it proves itself again. This is the single most important action and the one the exam always rewards.
- Report it. Notify the supervisor and follow the department's process for equipment failures. Failed tests get escalated, not quietly re-run.
- Investigate. Common causes: air leaks in the chamber or door gasket, steam quality issues like wet steam, problems with the vacuum system or drain, and operator setup errors. Maintenance gets involved.
- Document everything. Record the failure, the investigation findings, and the corrective actions. Sterility assurance lives on documentation.
- Retest after correction. Run the Bowie-Dick test again, correctly, and only return the sterilizer to service when it passes.
Note what is NOT on that list: running the test again immediately and hoping for a better sheet, processing loads "just this once," or treating the failure as a flaky indicator. The test failed for a reason, and the reason has to be found. Our Bowie-Dick test guide covers the test itself in more depth, and biological vs chemical indicators explains how the Bowie-Dick fits into the full monitoring hierarchy.
!How Bowie-Dick shows up on the exam
Bowie-Dick questions are some of the most predictable on the exam, which makes them free points if you know the patterns:
- "What type of sterilizer?" Dynamic-air-removal (prevacuum) steam. If the scenario says gravity, the Bowie-Dick does not apply.
- "When is it run?" Daily, before the first processed load. Not weekly, not after every load, not at the end of the day.
- "Where does the pack go?" Empty chamber, bottom shelf, over the drain. The exam will offer tempting wrong spots.
- "The test failed. What do you do?" Do not use the sterilizer. Report, investigate, document, retest. Never "run it again and see."
- "The sheet is patchy but the pack was expired." Invalid, not failed. Fix the setup and repeat. The exam loves punishing people who call every bad sheet a failure.