Bowie-Dick Test, Air Removal Testing, and Cycle Qualification — Sterile Processing Technician

Objective. Students will correctly perform and interpret a Bowie-Dick test and an air-removal/leak test on a prevacuum steam sterilizer, and document results on an equipment qualification log.

Why Air Removal Matters in Prevacuum Steam Sterilization

Prevacuum (pre-vac) steam sterilizers use one or more vacuum pulses before the sterilization phase to pull air out of the chamber and the load. This matters because air is a poor conductor of heat and, if trapped inside a pack or against a surface, it acts as an insulating barrier that prevents steam from reaching the item. An instrument wrapped inside an air pocket may never reach the required sterilization temperature, even though the sterilizer's printout shows a normal cycle. The result is a potentially non-sterile item delivered to a patient — a direct safety risk.

The Bowie-Dick test and the air-removal (leak) test are the two standard tools used every operating day to confirm that a prevacuum sterilizer is evacuating air correctly before any patient-care loads are processed.

The Bowie-Dick Test

The Bowie-Dick test was developed to detect air entrapment and air leaks in prevacuum steam sterilizers. It is not a biological indicator test and it does not assess lethality; its sole purpose is to evaluate the sterilizer's air-removal system.

What it consists of. A commercial Bowie-Dick test pack contains a chemical indicator sheet surrounded by a standardized mass of absorbent material (or a single-use equivalent). The chemical sheet changes color when exposed to steam uniformly.

How to run the test.

1. The test is run on an empty chamber — no other load items are present.

2. Place the test pack on the lowest shelf (or the shelf specified by the sterilizer and pack manufacturer), near the drain, in the front of the chamber. This is typically the most challenging location for air removal.

3. Select the specific Bowie-Dick test cycle on the sterilizer — usually a short prevacuum cycle at 134 °C (273 °F) for approximately 3.5 minutes; always follow the manufacturer's instructions for both the sterilizer and the test pack.

4. After the cycle completes, retrieve the pack and open it. Allow the sheet to cool briefly before reading.

Interpreting the sheet. A pass result shows a uniform color change across the entire indicator sheet with no light areas, streaks, or uneven patterns. A fail result may appear as:

A lighter or unaffected area in the center of the sheet, indicating air entrapment at the core of the pack.
Streaks or irregular lighter areas, indicating channeling or partial air removal.
Any non-uniform pattern should be treated as a failure.

The Air-Removal (Leak) Test

Some facilities run a separate air-removal or leak test (sometimes called a vacuum leak test) in addition to the Bowie-Dick test. This test verifies that the chamber door gaskets and plumbing are not allowing air to re-enter during the vacuum phase. The sterilizer draws down to a defined vacuum level, the pump is shut off, and the rate of pressure rise over a set time period is measured. The manufacturer specifies the acceptable leak rate. If the chamber pressure rises faster than allowed, air is infiltrating the system, and the sterilizer must be taken out of service. Follow your specific sterilizer manufacturer's instructions and your department policy for conducting and passing this test.

Frequency and Timing

According to widely accepted industry standards (including AAMI and HSPA guidance), a Bowie-Dick test should be performed each day the sterilizer is used, before the first processed load. This ensures that any malfunction is detected before patient-care items enter the sterilizer.

Equipment Qualification Logging

Documentation is not optional — it is a patient safety and regulatory requirement. Every Bowie-Dick test run must be logged immediately. A standard equipment qualification log entry includes:

Date and time
Sterilizer ID or number
Cycle number (from the sterilizer printout)
Type of test performed
Result (pass or fail)
Action taken if the result was a failure
Technician's signature or initials

Keep the used Bowie-Dick test sheet attached to or filed with the log entry for that cycle. Many facilities retain these records for a period defined by department policy or accreditation requirements.

Responding to a Failed Test

A failed Bowie-Dick result means the sterilizer must not be used for patient-care loads until the problem is identified and corrected. The correct sequence is:

1. Do not process any loads in that sterilizer.

2. Affix an out-of-service tag to the sterilizer door so no one inadvertently uses it.

3. Notify your supervisor immediately. You are not expected to diagnose or repair the sterilizer — that is outside your scope of practice.

4. Document the failure in the equipment qualification log, including the time, result, and that the supervisor was notified.

5. The sterilizer should not be returned to service until it has been inspected, repaired if necessary, and passes a requalification Bowie-Dick test (often three consecutive passing tests, per department policy).

Never attempt to override a failed result or quietly run a patient load anyway. A single non-sterile instrument can cause a serious surgical site infection.

Safety Summary

Always use an empty chamber for the Bowie-Dick test.
Read the indicator sheet under good lighting and compare it to a known pass and fail reference.
When in doubt about an ambiguous result, treat it as a failure.
Documentation must be completed before moving on — an undocumented test did not officially happen.

Key terms8

Bowie-Dick testA daily test run in an empty prevacuum steam sterilizer to confirm that air is being removed effectively from the chamber; uses a chemical indicator sheet that must show uniform color change to indicate a passing result.

Air entrapmentThe presence of residual air trapped inside a sterilizer chamber or within a pack that prevents steam from contacting surfaces, potentially leaving items non-sterile.

Prevacuum sterilizerA type of steam sterilizer that uses one or more vacuum pulses before the sterilization phase to actively remove air from the chamber and load.

Chemical indicator (CI)A device that uses a color-changing chemical reaction to show whether a specific sterilization parameter (such as steam exposure) has been met; the Bowie-Dick sheet is a Class 2 chemical indicator.

Air-removal (leak) testA test that measures the rate at which air pressure rises inside the sterilizer chamber after a vacuum is drawn, used to detect leaks in door gaskets or plumbing that could compromise air removal.

Equipment qualification logA written or electronic record documenting each test run on a sterilizer, including date, cycle number, result, and technician signature, maintained for accountability and regulatory compliance.

Out-of-service tagA physical label affixed to equipment that has failed testing or is otherwise unsafe to use, warning staff not to operate it until it has been inspected and cleared.

Uniform color changeA passing Bowie-Dick result in which the entire chemical indicator sheet shows a consistent color shift with no lighter areas, streaks, or uneven patterns, indicating complete and even steam penetration.

In class: Instructor demonstrates proper Bowie-Dick test pack placement (empty chamber, correct shelf position, correct cycle selection) and post-cycle sheet interpretation; students compare a series of five printed Bowie-Dick test sheets (one uniform color change, two with central light areas indicating air entrapment, two with streaks) and classify each as pass or fail. · Each student independently runs a Bowie-Dick test on the lab sterilizer, retrieves the test sheet, interprets the result, and completes the equipment qualification log entry including date, sterilizer ID, cycle number, result, and their signature. · Tabletop simulation of a failed Bowie-Dick result: students follow a written department policy flowchart to take the sterilizer out of service, notify the supervisor (role-played by instructor), affix an out-of-service tag, and document the event, then verbally explain the rationale for each step.
Materials: Prevacuum steam sterilizer, commercial Bowie-Dick test packs, printed Bowie-Dick comparison sheets (pass and fail examples), equipment qualification log forms, out-of-service tags, department policy flowchart handout, HSPA Central Service Technical Manual
Check: Instructor directly observes each student's independent Bowie-Dick run using a 10-point checklist (placement, cycle selection, interpretation, documentation); pass mark 8/10; any error in interpretation or documentation triggers immediate correction and a second attempt before the lesson closes.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.