Bowie Dick Test: Ready to Use Test Pack or Standard Test Pack (7kg of cotton sheet) according to EN 285?

Hi All,

I would like to have your opinion on the following: There are ready to use bowie dick test packs available (those 10 cm by 10 cm packs with paper and a test sheet in the middle). Are you putting these as a whole inside the autoclave, of do you follow the EN 285 norm, and take this test sheets out of the package and wrap it in 7 kg of cotton sheets?

EN 285 states in :

19 Bowie and Dick test
NOTE. The Bowie and Dick test was conceived as a test for successful air removal for so-called high-vacuum porous load sterilizers. A successful Bowie and Dick test indicates rapid and even penetration of steam into the test pack. Retention of air within the pack due to:
- an inefficient air removal stage;
- the presence of an air leak during the air removal stage;
. ’ - the presence of non-condensable gases in the steam supply;
are circumstances which can lead to failure of the test
The result of the test can also be affected by other factors which inhibit steam penetration. A failure of the test is therefore not conclusive proof that a fault is due to air retention, air leakage or non-condensable gases, and other causes of failure may need to be eliminated.
19.1 Apparatus
19.1.1 Standard test pack as described in 26.1.
19.1.2 Indicator in accordance with prEN 867-3.
19.1.3 Connected services complying with clause 13.
19.2 Procedure
19.2.1 Select the sterilization cycle to be tested (see 7.1.14).
19.2.2 Carry out a sterilization cycle with the sterilizer chamber empty and without any extended drying time.
19.2.3 Remove the wrapping from the standard test pack and place the indicator in the sheet located in the approximate centre of the standard test pack.
Reassemble and secure as described in 26.1.
19.2.4 Place the standard test pack above the nominal geometric centre of the horizontal plane of the usable space supported at a distance of between 100 mm
and 200 mm above the chamber base.
For sterilizers of one sterilization module the method shall be modified such that the standard test pack is supported above the base of the sterilizer chamber.
19.2.5 Carry out a sterilization cycle in accordance with the manufacturer’s operating procedure.
19.2.6 At the end of the test examine the indicator for compliance with the requirement specified in

26.1 Standard test pack
NOTE 1. This test, pack is used to check that, at the levels at which the process variables are set, rapid and even penetration of steam into the pack is attained.
NOTE 2. It is used for the Bowie and Dick test, the small load test, air detector tests, load dryness test, textiles and can be used with other materials to form a full load.

26.1.1 The test pack shall be composed of plain cotton sheets, each bleached to a good white and having an approximate size of 900 mm X 1200 mm. The number of threads per centimetre in the warp shall be (30 ± 6) and the number of threads per centimetre in the weft shall be (27 ± 5).**
26.1.2 The sheets shall be washed when new and when soiled and shall not be subjected to any fabric conditioning agent.
NOTE. Fabric conditioning agents can affect the characteristics of the fabric and can contain volatiles which will contribute to the non-condensable gases in the sterilizer chamber.
26.1.3 The sheets shall be dried and then aired for at least 1 h at a temperature of between 15 °C and 25 °C, with a relative humidity of 30 % to 70 %.
26.1.4 After airing, the sheets shall be folded to approximately 220 mm X 300 mm and stacked to a height of approximately 250 mm. After compressing by hand, the pack shall be wrapped in similar fabric and then secured with tape not exceeding 25 mm in width. The total weight of the pack shall be 7 kg ± 10 %.
NOTE 1. Packs which are not used within 1 h of preparation can be stored in the work-room, provided the environmental conditions are maintained within the limits specified above. NOTE 2. After use, the sheets will become compressed. When the weight of sheets used to form a stack 250 mm high exceeds 7,7 kg, the sheets should be discarded.
26.1.5 Test packs comprising different materials and of different sizes and weights can be used, provided equivalence with the requirements for the test in which the standard test pack is used is demonstrated
***(see 17.1, 18.1, clause 19, 21.1, 21.3 and 22.1).

I’ve always just used the packs as they come in a kit. Anybody else?

Hi Monepoc
Single use Bowie & Dick packs are fine when used for the Bowie & Dick test. Make sure that the packs conform to relevant standard.
The test sheet should NOT be removed from a paper pack and placed in the STP 7kg pack. They are designed specifically for use intact as they are.
Some manufactures sell individual test sheets that are designed for use in the standard test pack. Most people use single use paper packs as it is less time consuming.
Single use paper B&Ds can NOT be used for any of the thermometric tests because the test probes provide a path for steam and air to track down the sides of the probes. I.E. They will not seal properly around the probes. The cotton STP should be used for these tests.
There are also electronic versions available (ETC) but can be expensive.

As you have mentioned in EN-285 it is clearly stated B-D test is conceived for “high-vacuum porous load sterilizers”, mainly pack of clothes and others made on tissue. There are persons giving this test other meaning by generalizing it for any load in order to estimate heat penetration determination, which can give false results.