Air Removal Tests, Biological Indicators and PCDs

Dynamic Air Removal Testing: Bowie-Dick and DART

In pre-vacuum steam sterilizers, air must be actively removed from the chamber so that steam can contact every surface of the items being processed. A Bowie-Dick test evaluates the efficacy of dynamic air removal in pre-vacuum steam sterilizers. This test detects air leaks, inadequate air removal, and the presence of non-condensable gases that can prevent steam from sterilizing instruments. The Daily Air Removal Test, or DART, is a commercially manufactured equivalent of the Bowie-Dick test. Technicians should note that Bowie-Dick testing is not applicable to gravity-displacement steam sterilizers, which rely on passive air displacement rather than mechanical dynamic air removal.

Air removal testing must be performed daily in dynamic air-removal steam sterilizers. A Bowie-Dick test should be run each day the sterilizer is used, typically before the first processed load of the day. When required by the sterilizer manufacturer's instructions for use, such as after the sterilizer has been shut down, a warm-up cycle must be run before the Bowie-Dick test. Before conducting the test, sterile processing technicians must verify the expiration dates of the Bowie-Dick test packs to ensure the chemical indicators are valid.

The Bowie-Dick test pack must be run in an otherwise completely empty sterilizer chamber. In a pre-vacuum steam sterilizer, the technician places the test pack horizontally over the drain on the bottom rack. After the cycle finishes, the test sheet inside the pack is evaluated. A uniform color change throughout the Bowie-Dick test sheet indicates a passing air removal test. If residual air is present in the chamber, it may produce a lighter or unchanged area, often near the center of the Bowie-Dick test sheet, indicating a failed test that must be addressed.