Quick answer: A Bowie-Dick test confirms that a pre-vacuum sterilizer has removed air from the chamber before the cycle begins. In Canada, the test is expected at the start of every day the sterilizer is used, and again after any repair or major change that could affect air removal. In the United States, AAMI ST79 and CDC guidance describe the same daily expectation for pre-vacuum and dynamic-air-removal units. Gravity-displacement sterilizers do not use a Bowie-Dick test at all, so the whole question only applies to vacuum-assisted machines.
What does the Bowie-Dick test actually check?
The Bowie-Dick test is an air-removal test, not a sterility test. It uses a chemical indicator sheet inside a standard test pack placed horizontally near the chamber drain. During the cycle, steam must penetrate the pack evenly and change the indicator to a uniform dark colour. A pattern that is mottled, pale, or lighter in the centre means air was trapped and the load was not exposed to saturated steam evenly.
Because the test targets air removal rather than microbial kill, a passing sheet does not prove that instruments are sterile. That judgement comes from the rest of the monitoring chain: chemical indicators on each package, biological indicators for load release, and a complete physical record of time, temperature and pressure for every cycle.
Which sterilizers need a Bowie-Dick test every day?
Only pre-vacuum (class B) and dynamic-air-removal sterilizers need one. These machines pull a vacuum before admitting steam, and any leak in the door gasket, valve or pump can leave air behind. A gravity-displacement sterilizer relies on gravity to push air out and does not perform an air-removal stage, so a Bowie-Dick pack is not meaningful on that unit.
Practically, that means a dental office running a class B tabletop unit should treat the Bowie-Dick test as part of the morning start-up routine, alongside the warm-up cycle and the chamber drain check. A clinic with a gravity unit skips this step and relies on the daily biological indicator instead.
| Item | Canada | United States |
|---|---|---|
| Applies to | Pre-vacuum / dynamic-air-removal sterilizers (class B) | Same — pre-vacuum and dynamic-air-removal units |
| Usual frequency | Each day the sterilizer is used, before the first load | Each day the sterilizer is used, before the first load |
| After repair | Repeat before returning the unit to service | Repeat before returning the unit to service |
| Reference framework | Provincial IPAC guidance and CSA Z314 series | AAMI ST79 and CDC guidance |
| Record kept | Signed cycle log with the test result | Logged result retained with cycle records |
How often does Canada require the test compared with the US?
On air-removal testing the two countries are close, and that is worth stating plainly because a lot of clinic documentation mixes the standards up. Canadian provincial infection-control guidance, the CSA Z314 series, and the equivalent American documents all treat the Bowie-Dick test as a daily pre-use check for vacuum sterilizers. The difference is not in the frequency; it is in which document an inspector will ask you to cite.
A Canadian clinic should be able to point to its provincial guidance and the CSA Z314 family, while a facility reporting to an American accreditation body will cite AAMI ST79. Writing the wrong jurisdiction onto the log is a documentation finding even when the test itself was performed correctly. That single error is one of the most common issues uncovered during mock audits.
What does a failed Bowie-Dick test mean, and what should you do next?
A failed test means the load that follows cannot be released. Stop the sterilizer, do not run patient instruments, and work through the likely causes in order: a door gasket that no longer seals, a blocked or dirty chamber drain filter, a worn vacuum pump, an overfilled chamber, or a test pack that was reused beyond its limit. Re-run a fresh pack only after you have addressed a plausible cause.
If the repeat test also fails, remove the unit from service and arrange a service call. Keep the failed indicator sheets — they are evidence that your monitoring system worked as designed. A record of a failed test followed by a documented repair and a passing retest is a stronger audit position than a log with no failures at all.
How does the Bowie-Dick test relate to biological indicator monitoring?
The two tests answer different questions, and a clinic needs both. The Bowie-Dick test asks whether steam reached the whole load evenly; a biological indicator asks whether the cycle actually killed a resistant spore population. In Ontario, the RCDSO expects a biological indicator for each sterilizer on every day it is used — daily monitoring, not weekly. The weekly baseline is the CDC and AAMI ST79 pattern in most US states, which is why the two schedules are so often confused.
For a pre-vacuum unit that runs every weekday, a realistic consumable plan is one Bowie-Dick pack and one biological indicator per day, five days a week, about fifty weeks a year. That is roughly 250 indicators a year for a single sterilizer. Building that number into the annual budget avoids the mid-year scramble that happens when a clinic finally counts how many tests it should have run.
Related reading
Sterilization compliance hub; air removal testing on pre-vacuum autoclaves; spore test frequency in Canada vs the US; spore test log fields; BI 5-pack trial; sterilization monitoring collection.
Download the cycle and spore test templates from the compliance log centre, run the sterilization self-check to see which daily tasks your clinic is missing, and book a sterilization compliance consultation if a recent audit flagged your monitoring records.
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Frequently Asked Questions
Do gravity sterilizers need a daily Bowie-Dick test?
No. A Bowie-Dick test measures air removal, and gravity-displacement sterilizers do not have an air-removal stage. Those units rely on the daily biological indicator and chemical indicators instead.
Can I reuse a Bowie-Dick test pack?
No. Reuse is one of the most common causes of a failed result, because the pack no longer behaves like a fresh load. Use a new pack for each test and record the lot number.
What do I do if the Bowie-Dick test fails twice?
Remove the sterilizer from service, keep the failed indicator sheets, and arrange a service call. Do not release any load processed on that unit until a repeat test passes.
Is the Bowie-Dick frequency different in Canada and the US?
The daily pre-use expectation is effectively the same for pre-vacuum units. What differs is the document a clinic cites — Canadian provincial IPAC guidance and the CSA Z314 series, versus AAMI ST79 and CDC guidance in the United States.
CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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