Bowie-Dick Testing: How to Respond to a Vacuum-Sterilizer Test Failure

In a vacuum-type or prevacuum steam sterilizer, effective air removal is necessary for steam to contact the surfaces of the test challenge and the items being processed. A Bowie-Dick test is used to assess air removal and steam penetration in an empty chamber before routine processing begins. It is not a sterility test for a completed load and does not replace routine mechanical, chemical, or biological monitoring.

A result outside the test manufacturer’s acceptance criteria indicates that air removal or steam penetration was inadequate under the specified test conditions. The result does not, by itself, identify the exact cause. The appropriate response is to control the situation, verify the test method, and investigate the equipment and process before the sterilizer is returned to routine use.

What the Bowie-Dick test assesses

CDC identifies the Bowie-Dick test as a daily air-removal test for prevacuum steam sterilizers. The test is performed in an empty chamber before the first processed load of the day.[1]

The test challenge includes a chemical indicator that responds to steam penetration through the challenge. A uniform endpoint generally indicates that the test conditions allowed steam to reach the indicator throughout the challenge. A nonuniform pattern, light area, spot, or other result outside the test manufacturer’s acceptance criteria may indicate inadequate air removal or incomplete steam penetration.[2]

The result should be understood as evidence about sterilizer performance under the specified test conditions. A passing result does not prove that every item in a later load is sterile. It also does not confirm that loading, packaging, cleaning, exposure, drying, or handling requirements were met.

When and how to perform the test

Perform the test each day the vacuum-type or prevacuum steam sterilizer is used, before the first processed load. Use the test device, orientation, chamber location, cycle, and interpretation method specified by the test-device manufacturer and consistent with the sterilizer manufacturer’s requirements. The test should not be adapted from a general reference when those instructions differ.

CDC material describes placing a Bowie-Dick-type test in the front, bottom portion of the chamber near the door and over the drain, using the specified test cycle.[2] The applicable instructions for the particular test system and sterilizer should govern the actual setup.

Before running the test, confirm that the chamber is configured as required by the test-device instructions and the sterilizer’s operating requirements. Do not assume that a chamber arrangement, cycle, or placement used for one test system applies to another.

Interpreting the result

Passing result

A passing result is one that meets the test manufacturer’s defined acceptance criteria. Document the result in a record linked to the date, sterilizer identification, operator, and test lot or device identification where applicable. A pass supports proceeding according to the facility’s routine processing procedure, but it does not replace the monitoring required for individual loads.

Failing or indeterminate result

If the result is outside the acceptance criteria, or if the operator cannot interpret it confidently, place the sterilizer on hold. Do not process or release routine loads solely because the display or printout appears normal. A failed air-removal test may identify a problem that is not apparent from the basic time, temperature, or pressure record.

Investigation should first consider whether the test was selected, prepared, placed, and interpreted correctly. Other possible contributors directly relevant to the test include air leaks, inadequate air removal, and problems that prevent appropriate steam contact with the test challenge. These are investigation considerations, not conclusions established by the Bowie-Dick result alone.

Review the test method together with the equipment record, maintenance history, operator technique, cycle information, and any facility trend data. A repeat test may be appropriate after confirming that the correct test, cycle, placement, and interpretation method were used. A quick repeat without addressing a possible setup or equipment issue can create false reassurance.

What to do after a failed test

1. Hold the sterilizer. Do not process or release routine loads until the failed or indeterminate result has been assessed.
2. Document the event. Record the test result, test identification, sterilizer, date, operator, cycle used, and immediate actions.
3. Verify the method. Confirm that the test was appropriate for the vacuum-type or prevacuum sterilizer, that the chamber and test setup met the applicable instructions, and that the required cycle was used.
4. Review recent activity. Check maintenance and repair records, alarms, cycle records, unusual test patterns, and other information required by the facility’s procedure.
5. Escalate when indicated. If the failure is confirmed or cannot be explained by test setup, follow the facility’s equipment-failure procedure and contact qualified maintenance personnel.
6. Return to service only after acceptance. Follow the facility’s written quality-system procedure for inspection, repeat testing, any additional checks, and authorization to resume use.

CDC instructs that a sterilizer that fails the air-removal test should not be used until it has been inspected by maintenance personnel and passes the test.[3] Requirements concerning quarantine of items, additional testing, documentation, and formal return-to-service authorization should be taken from the facility’s written procedure, the applicable equipment and test-device instructions, and other requirements governing that facility.

Why a normal printout does not override a failed test

Mechanical records show whether selected cycle parameters were reached or displayed. They do not necessarily demonstrate that air was removed from every part of the test challenge or that steam penetrated the challenge as intended. The Bowie-Dick test addresses a different question: whether air-removal and steam-penetration performance was acceptable under the specified test conditions.

These monitoring approaches are complementary rather than interchangeable. A normal mechanical record cannot cancel a failed chemical air-removal test. Conversely, a passing Bowie-Dick test cannot compensate for an inadequate exposure cycle, incorrect load configuration, failed internal chemical indicator, damaged package, or other load-specific problem.

Important limitations

The Bowie-Dick test is not designed to validate every load configuration. It can indicate inadequate air removal or steam penetration under the test conditions, but it does not establish that a particular device, lumen, package, or load was adequately sterilized. Where a load presents a specialized challenge, the facility should determine whether an appropriate process challenge device or other validated method is required, using applicable manufacturer instructions and written procedures.

Repeated borderline or abnormal results should be handled according to the facility’s investigation and trending procedure. Trend information can help the facility identify recurring test or equipment concerns, but trending does not replace evaluation of an individual failed or indeterminate result.

Practical checklist for sterile processing teams

• Use the Bowie-Dick test each day a vacuum-type or prevacuum steam sterilizer is used.
• Run it before the first processed load, using the chamber setup required by the applicable instructions.
• Use the specified test device, cycle, placement, and acceptance criteria.
• Record the result so it can be linked to the sterilizer, operator, date, and test identification.
• Hold the sterilizer after a failed or indeterminate result.
• Do not release loads based only on a normal mechanical printout.
• Verify test selection, setup, placement, cycle, and interpretation.
• Investigate possible air-removal, air-leak, and steam-contact problems.
• Escalate confirmed or unexplained failures to qualified maintenance personnel.
• Follow the facility’s written procedure for additional testing and return to service.

Educational disclaimer: This article provides general educational information for sterilization and sterile processing professionals. It does not replace the sterilizer manufacturer’s instructions, the test-device manufacturer’s instructions, validated facility procedures, applicable requirements, or qualified technical assessment.

References

1. Sterilizing Practices. Centers for Disease Control and Prevention. 2023-11-28.
2. Steam Sterilization. Centers for Disease Control and Prevention. 2023.
3. Guidelines for Infection Control in Dental Health-Care Settings—2003. Centers for Disease Control and Prevention. 2003-12-19.

Educational overview. Follow the applicable product instructions, validated procedures, local regulations and your facility’s approved policies.