Ensuring that you have an effective and safe decontamination and sterilisation process is crucial to ensure patient and staff safety in your veterinary practice.

There are several factors to take into consideration when reviewing and implementing your surgical instrument sterilisation process. You can download our full guide to surgical instrument decontamination and sterilisation here.

In this post, we will focus on one of the key parts of your sterilisation process and how you can monitor it effectively – your steriliser. You can have all the right processes in place but if your steriliser is not operating effectively, your instruments will of course not be sterile! We rely heavily on our sterilisers to operate according to the correct parameters and therefore we need to have a consistent and effective testing and verification process in place to identify any potential issues with our equipment.

We will now explore the implementation and use of a Bowie Dick test: what is it, why do we use it and how can it help us improve instrument sterilisation in the veterinary practice?

We are all familiar with a TST test strip, the small verification strips we use on an ongoing basis in our sterilisers.


STERIS Albert Browne TST Test Strips for steam sterilisers
STERIS Albert Browne TST Test Strips for steam sterilisers


TST stands for Temperature, Steam and Time and is a test used to confirm that a certain temperature has been achieved for a specified amount of time.

Autoclaves, however, rely on several other parameters in order to deliver an effective sterilisation process. Whilst a TST test strip is needed in every cycle to confirm temperature and holding time, it does not identify other potential issues with the cycle.

Let’s take a closer look at the basics of a steam steriliser utilising a pre-vacuum cycle.

For us to be able to class something as “sterile” using steam sterilisation we need to achieve a certain temperature for a certain period of time. The most common cycle is a cycle of 134-137°C for 3 – 3.5 minutes. Another key part of the cycle is steam penetration, high-temperature steam needs to penetrate the packaging (pouch, wrap or container) and reach every little millimetre of your instrument to ensure sterility. To ensure effective steam penetration, we rely on the ability of the steriliser to effectively remove air before injecting moist steam. Pockets of air within the steriliser can result in an ineffective sterilisation cycle – 1mm of air has the same insulation properties as a brick under the high temperatures within the sterilisation cycle. Trapped pockets of air can, therefore, be a serious risk and can prevent the effectiveness of the sterilisation process. We, therefore, need to ensure that the machine is capable of effectively removing all air within the chamber.

A pre-vacuum autoclave removes air in several pulses prior to injecting steam into the chamber. If this air removal sequence is not working properly, we risk having trapped pockets of air within the chamber. When steam is injected this trapped air can reduce the steam penetration capabilities due to its insulating properties at high heat.
This is one of the key purposes of a Bowie Dick test, to test the steam penetration within the steriliser. Our TST test strip does not test for steam penetration, we can have sufficient temperatures within the sterilisation chamber but if there is trapped air we will not have an efficient cycle and we risk non-sterile items. Within the healthcare sector, completing a daily Bowie Dick test is a regulatory requirement due to the risks associated with inefficient air removal in sterilisers.


Illustration of the different process verification products (Bowie Dick and TST test strip)
Illustration of the different process verification products (Bowie Dick and TST test strip)

Selecting the Right Test for Your Steriliser

The STERIS Albert Browne Bowie Dick test is suitable for large chamber steam sterilisers to confirm efficient air removal. The product comes in a box of 20 and should be used daily to verify the effective air removal of your steriliser.


STERIS Albert Browne Bowie Dick test for large sterilisers
STERIS Albert Browne Bowie Dick test for large sterilisers


If you have a smaller steriliser which self-generates steam, the properties of the cycles are slightly different. The air removal and warm up is slower and therefore you need to use a different type of air removal test, this is known as a Helix Device. STERIS Albert Browne’s TST Helix tests are specifically developed for small sterilisers and available to purchase from STERIS Animal Health. The air removal tests (Bowie Dick or TST Helix) follow the same principles as a STERIS Albert Browne TST test strips with an easy to read visual indicator sheet turning from Yellow to Blue to indicate a pass.


STERIS Albert Browne TST Helix for small sterilisers
STERIS Albert Browne TST Helix for small sterilisers

Let’s Recap:

  • Ensuring that you test your steriliser daily is crucial to patient safety, unsterile instruments can cause severe harm to patients and staff.
  • To confirm the effectiveness of our sterilisers we need to not only test time and temperature, we also need to confirm efficient air removal.
  • Pockets of air, regardless of how small reduce steam penetration and can lead to unsterile instruments.
  • Select a Bowie Dick test suitable for your steriliser. The STERIS Albert Browne Bowie Dick test should be used for large chamber steam sterilisers while the TST Helix is suitable for smaller chambers.
  • Use the Bowie Dick or TST Helix test daily, preferably at the start of the day.

Want to learn more about instrument sterilisation? We arrange CPD events for both vets and vet nurses! Keep an eye out on our social media channels and website for upcoming events.

Have questions relating to decontamination and sterilisation? We are always here to provide support, just email us with your questions!

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