A process challenge device is a test item built to resist the sterilization process more than the load does, so that a pass result means the hardest place in the load also got sterilized. A pouch is not a process challenge device: the pouch is a sterile barrier that protects the contents after the cycle, while the challenge device is a test that measures whether the cycle worked. Confusing the two is the reason some clinics believe a colour-change pouch stripe is a sterility test. Our 24-hour self-contained biological indicators list at $109.99 for 50 and are the biological half of that challenge.
What is a process challenge device and what does it do?
The term comes from sterilization standards and describes an item designed to present a defined challenge to the process: something that is harder for steam to penetrate and air to leave than an ordinary instrument would be. The point is sensitivity. If you test with an easy item, a failing cycle can still produce a pass, because the conditions reached the easy item first. A challenge device is deliberately the worst case, so a pass there is evidence about the whole load.
| Item | Purpose | What a result tells you |
|---|---|---|
| Pouch or wrap | Sterile barrier system | Protects contents after the cycle; the indicator stripe shows exposure only |
| Chemical indicator | Detects one or more cycle parameters | That the indicator saw the conditions it is designed to react to |
| Biological indicator | Contains spores of a defined resistance | Whether the process killed the most resistant organisms present |
| Process challenge device | Holds a BI or CI in a defined worst-case configuration | Whether the process penetrated the hardest location in the load |
| Bowie-Dick test pack | Air removal and steam penetration test for pre-vacuum cycles | Whether air was removed uniformly across the chamber |
Note what the challenge device is not. It is not a bigger pouch, and it is not a substitute for the barrier. A pouch with a Class 4 indicator inside is a package with a chemical indicator; a challenge device is a separate item placed in the load precisely because the package cannot test itself.
How is a process challenge device used in a normal cycle?
Place it where the process is hardest: the centre of the load, inside a wrapped tray or cassette, or the position the sterilizer manufacturer identifies as the least favourable. Running it on the empty top shelf tests the easiest location, which tells you almost nothing. One device per load is the common clinic practice for biological monitoring, and the device travels with the load record so a positive result can be traced to the items that were in that cycle.
Read the result at the time the indicator specifies. A 24-hour biological indicator read early is not a result; a rapid-readout fluorescence indicator read without its reader is not a result either. If your clinic runs both a rapid screen and a 24-hour confirmation, document which one released the load, because the record has to show a release decision, not just two numbers.
Does a challenge device replace the Bowie-Dick test?
No. The Bowie-Dick test is specifically an air-removal and steam-penetration test for pre-vacuum cycles, run at the start of the day before the first load; it does not contain spores and cannot tell you about lethality. A biological challenge device tests the kill. A clinic running pre-vacuum cycles needs both kinds of evidence, and a clinic running gravity cycles does not run a Bowie-Dick test at all, because the test is designed for the air-removal behaviour of pre-vacuum machines.
Where clinics get into trouble is substitution under time pressure: the Bowie-Dick passed, so the spore test is skipped "just this once". The two tests answer different questions, and an inspector will ask for both records.
What should a clinic document?
Five fields per monitored load: the date and cycle number, the sterilizer identifier, the challenge device lot, the result and the time it was read, and the release decision with the initials of the person who made it. Add the load contents or a reference to the tray list, so a positive can be traced to specific instruments. If the result is positive, the load is quarantined, the sterilizer is taken out of service, and the recall and retest sequence follows your policy — the records from before the positive are what an inspection will read first.
The printable sterilization log sheets carry those five fields and a quarantine block, and the sterilization self-check will show whether the fields are consistently filled or only on the days someone remembers. If your challenge device placement or your release policy has never been reviewed against the current guidance, ask a compliance specialist to walk through it. Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing, and the sterilization monitoring collection groups the indicators, tape and pouches that support this record set. Reselling? become a distributor.
Related Reading
- What Is a Biological Indicator? Definition, Organism and Formats
- After a Failed Spore Test: Quarantine, Retest and Release
- What Does a Class 4 Chemical Indicator Actually Measure?
Frequently Asked Questions
Is a sterilization pouch a process challenge device?
No. A pouch is a sterile barrier system. A process challenge device is a separate test item built to present a defined worst-case challenge to the process.
Where should a process challenge device be placed in the load?
In the least favourable location for steam penetration — typically the centre of the load or inside a wrapped tray — not on an empty shelf.
Does a Bowie-Dick test replace biological monitoring?
No. Bowie-Dick tests air removal and steam penetration in pre-vacuum cycles; it contains no spores and says nothing about lethality.
What has to be recorded for each monitored load?
Date and cycle number, sterilizer identifier, challenge device lot, result and read time, and the release decision with initials. Add a reference to the load contents.
Last updated: October 2026. CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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