The document provides information on Bowie Dick tests used to detect air in steam sterilization autoclaves. It describes how paper and electronic Bowie Dick tests work, potential causes of test failures, and specifications from ISO 11140. Paper tests use chemical indicators that change color with sufficient steam exposure, while electronic tests provide pass/fail results from temperature and pressure sensors. Failures may be due to issues with steam distribution, quality, or autoclave leaks and performance. ISO 11140 provides standards for Bowie Dick test pack configuration and performance.

1. Bowie Dick Tests
Failure Modes and Specification

2. Autoclave
Basic overview of how a Porous Load Steam Steriliser works
Steam pressure is controlled ensure
the drain is the correct temperature.
Baffle plates force steam to displace
air, down the drain.
Air is removed from the chamber, the presence of residual air can impact the sterilisation process. Bowie Dick
Tests are used as a daily test to detect air within the chamber.

3. Bowie Dick Test
Electronic Bowie Dick Tests use
temperature and pressure sensors to
identify residual air.
A Pass/Fail result is given when the Data is
downloaded
Bowie Dick Tests are a daily test used in autoclaves to detect air leaks.
Paper based bowie dick tests use a
chemical indicator which requires
Time, Steam and Temperature to
change colour.
They are available in 121 and 134°C.

4. Bowie Dick TestFailures
Passed Cycle
Failed Cycle
Paper Bowie Dick Test will show a full uniform
colour change in line with the manufacturers
guidelines (Colours will differ between
Manufacturers).
Electronic Bowie Dick Tests will display a Passed
or Failed result on download of the data.
Paper Bowie Dick Tests will not show a full
uniform colour change. This test has failed
and the cause of failure should be
investigated.
Electronic Bowie Dick Tests will show a Passed
or Failed result on download of the data.

5. Potential Causesof aBowie Dick TestFailure
Bowie Dick Failures can be caused by several factors:
Steam Distribution / Steam Quality Issues
• Superheat
• Perform Superheat Steam Quality Test
• Non Condensable Gases
• Perform NCG Steam Quality Test
Autoclave
• Check the Time at Temperature
• High Chamber Leak
• Perform Leak Rate Test

6. Potential Causes
Steam Distribution / Steam Quality
Step 1
Perform Steam Quality Testing (EN285:2015, PDA Technical Report 1)
• At Point of Use
• At Point of Generation
Step 2
Perform a Distribution Survey
• Check Steam Traps
• Pipe levels etc

7. Potential Causes
Autoclave
Check the process report to ensure the cycle
operated correctly with no alarms and the
correct exposure time.
Perform an initial leak rate, to establish if
this is the cause of the failure. If the leak is
high:
• Check and tighten clamps and gaskets
• If there is an induced leak on the
chamber, ensure it is isolated.
• Perform the leak rate again to confirm a
resolution.
Note: Leaks outside the leak test boundary
can also cause failures in Bowie Dick Tests,
for air detector clamps.

8. Bowie Dick Tests
ISO 11140

9. Bowie Dick Tests
Chemical Indicators – ISO 11140 Class 2
The specifications of Bowie Dick Tests are detailed in
ISO-11140 ‘Sterilisation Healthcare Products –
Chemical Indicators’.
This outlines the performance of the chemical
indicator used in the pack.

10. Bowie Dick Tests
There are three different sections within ISO
11140 for Bowie Dick Tests:
ISO 11140-3
ISO 11140-4
ISO 11140-5
Chemical Indicators – ISO 11140 Class 2

11. Bowie Dick Tests
ISO 11140-3
This Bowie Dick Test requires the use of a Standard
Towel Pack. The Indicator sheet is positioned in the
centre of the pack.
The test is very good, however it often isn't practical
to perform this as a daily bowie Dick Test Pack.
Chemical Indicators – ISO 11140 Class 2

12. Bowie Dick Tests
ISO 11140-4
Test packs that meet ISO 11140-4,typically have an
indicator sheet in the middle of a stack of paper.
They are challenged to display a failed result when a
leak into the chamber would temperature depression
within a standard towel pack of ≤2.0°C at the end of a
90 Second Equilibration.
Chemical Indicators – ISO 11140 Class 2

13. Bowie Dick Tests
ISO 11140-5
Bowie Dick Tests conforming to ISO 11140-5 are tested
using an alternative reduced Test Pack.
An ISO 11140-5 Bowie Dick Test is required to have a
≤2.0°C Depression between the centre of the pack and
the drain, in the last minute of a 3.5min cycle at 134°C
or in the last 5 minutes of a 15 minute cycle at 121°C
Chemical Indicators – ISO 11140 Class 2

14. Bowie Dick Tests
Chemical Indicators – ISO 11140 Class 2
For a robust air removal challenge, we recommend using a
ISO 11140-3 or ISO 11140-4 Bowie Dick Test Pack.
If you experience failures using this pack, the air removal
or conditioning phase of your autoclave cycle should be
optimised.
For more information on this please contact Thermal
Compliance Ltd or visit our training website
www.thermalcompliance.com

15. 0201
ABOUT US
We deliver practical and online
training courses in:
• Autoclave Validation
• Temperature Mapping
• Steam Quality Testing
• Kaye Validator 2000
Training
We can help with:
• Wet Loads
• Superheat Investigations
• Equilibration Failures
• Steam Quality Failures
• Biological Indicator Failures
Consultancy 03We perform Validation on a
wide range of equipment:
• LN2 Freezers – Ovens
• Autoclaves and SIP
• Freeze Driers
• Dry Heat Processes
Validation

16. CONTACT US
Chris Maughan
Managing Director
Thermal Compliance
chrism@thermalcompliance.co.uk
www.thermalcompliance.co.uk
18 Harelands Courtyard Offices
Moor Road Melsonby
Richmond
DL10 5NY
UK
Tel +44 (0)1748 327 247
www.thermalcompliance.com
(Training Website)