Autoclave · Calibration procedure
Bowie-Dick test
A daily test for pre-vacuum autoclaves that checks air removal and steam penetration, using a standard test pack containing a chemical indicator sheet that changes colour uniformly only if steam has penetrated fully.
PURPOSE
Why this is checked
Porous loads such as garments and wrapped filters are sterilised only if air is fully removed. A leaking door seal, a weak vacuum pump or non-condensable gases leave an air pocket in the centre of the pack, which shows as a pale or uneven area on the indicator sheet.
Frequency
Daily, before the first porous load, after the warm-up cycle; also after maintenance on the vacuum or steam systems.
Learn how the Autoclave worksYOU WILL NEED
Standards & tools
- Commercial Bowie-Dick test pack conforming to ISO 11140-4 / ISO 11140-5, or a standard towel pack with indicator sheet
- Within its expiry date and stored as the supplier recommends
BEFORE YOU START
Prerequisites
- Run a warm-up (empty) cycle first so the chamber is hot
- Chamber otherwise empty
PROCEDURE
Step by step
- 1Place the test pack on its own, horizontally, on the bottom shelf near the door above the drain, unless the manufacturer specifies otherwise.
- 2Run the Bowie-Dick cycle (typically 134 °C for 3.5 minutes; do not extend the time).
- 3Remove the pack at the end of the cycle with heat-resistant gloves and take out the indicator sheet.
- 4Examine the sheet: the colour change must be uniform from centre to edge.
- 5Record the result, attach the sheet (or a photograph) to the log, and keep the cycle printout.
RECORD
Example observation table
| Date | Cycle no. | Temperature / time | Colour change | Result |
|---|---|---|---|---|
| 03-Nov-2026 | 1452 | 134.2 °C / 3.5 min | Uniform dark colour across the sheet | Pass |
| 04-Nov-2026 | 1460 | 134.1 °C / 3.5 min | Uniform dark colour across the sheet | Pass |
| 05-Nov-2026 | 1468 | 134.3 °C / 3.5 min | Paler patch at centre | Fail |
CALCULATION
How to calculate the result
No numeric calculation: pass or fail by visual comparison of colour uniformity between the centre and the edges of the indicator sheet.
- 05-Nov-2026: centre of the sheet visibly paler than the edges
- Interpretation: air was not fully removed from the centre of the pack
- Result: Fail; porous cycles blocked until investigated and a repeat test passes
ACCEPTANCE CRITERIA
Pass if
- Uniform colour change across the whole indicator sheet, matching the manufacturer's pass example.
- Cycle parameters (temperature and time) as specified for the test.
IF IT FAILS
What to do
- Do not run porous or wrapped loads.
- Repeat the test once to rule out a handling error; if it fails again, label the autoclave out of use.
- Carry out a vacuum leak test, inspect the door gasket and check steam quality.
- Get the autoclave serviced and pass the Bowie-Dick test before releasing it for use.
MORE
Other Autoclave calibrations
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.