Bowie Dick test explained: how to run it daily and read the result

What the Bowie-Dick test actually checks

In a prevacuum steriliser, air is pumped out before steam is admitted. Air that remains in the chamber or in a porous load forms pockets that steam cannot reach, so surfaces inside are not exposed to the right temperature. The Bowie-Dick test, a class 2 indicator system under ISO 11140, is designed to detect air leaks, inadequate vacuum and non-condensable gases, which could produce those pockets.

It is a test of the steriliser's air removal and steam penetration, not a test of sterility. A pass does not prove that a given load was sterilised; it shows that the machine can remove air properly under test conditions. For other controls see sterilization indicator types.

Bowie dick test procedure

The test uses a standard test pack or an electronic or disposable test device that contains a chemical indicator sheet. Run it on an empty chamber at the specified short cycle, typically with a hold at the sterilisation temperature of 134 °C for a few minutes, as stated by the test manufacturer. Place the pack on the lowest shelf near the door, above the drain.

Do not run the test with other items in the chamber, unless the instructions allow it.

• Run the test before the first processed load of the day, after warm-up.
• Follow the test pack manufacturer's instructions for cycle and time.
• Remove the pack immediately after the cycle and let it cool before reading.
• Read the indicator in good light and compare with the supplied reference.
• File the sheet with date, steriliser ID and operator signature.

How to read the result: pass or fail

A pass is a uniform colour change across the whole indicator sheet, as described by the test manufacturer. A fail shows an uneven change, with a lighter patch in the centre, which indicates trapped air. Any doubtful sheet should be treated as a fail.

If the result is a fail, the steriliser is taken out of service until the cause is found and a repeat test passes. Typical causes are a leak in the door seal or pipework, a faulty vacuum pump, poor steam quality or an incorrect test pack. Tell biomedical engineering, check the door gasket first, and record the event. Loads processed since the last passing test must be assessed according to your recall SOP, as described in autoclave validation guidelines.

Helix test and B-type autoclave validation tests

A helix test, or PCD, uses a long hollow tube with an indicator at the end to challenge steam penetration into lumens, and is used for hollow instruments and small B-type sterilisers conforming to EN 13060. It is not a substitute for the Bowie-Dick in large hospital sterilisers, and the type of load defines which test fits.

B-type small sterilisers with fractionated vacuum are validated with helix or equivalent tests per their manual and local policy. If your CSSD handles laparoscopic or other lumened instruments, add a PCD in the load; see laparoscopic instrument reprocessing. The autoclave validation test regime also includes biological indicators and periodic revalidation.

Frequency, records and training

The usual routine is daily, before the first load, on each prevacuum steriliser, with additional tests after installation, repair or service on the vacuum system. Keep the sheets or electronic records with the load log. For layout of a full daily routine see CSSD checklist and SOP.

Make sure staff are trained to read the sheet and to escalate. Beckfinity's specialists can advise on containers and accessories that fit validated loads in your steriliser.