HTM 01-05 requires daily steam penetration tests (Helix or Bowie-Dick) for vacuum sterilisers before the first load, plus automatic control tests for all benchtop sterilisers. Every machine must have its own dedicated logbook. This guide details the testing types, frequencies, and documentation obligations under UK standards.
Sterilisation control operates at three complementary levels. Physical indicators are the parameters displayed by the autoclave (temperature, pressure, duration) — they confirm that the cycle ran according to the selected programme. Chemical indicators (autoclave tape, chemical integrators) change colour when exposed to sterilisation conditions. Biological indicators (spore tests) are the most reliable: they confirm that the most resistant micro-organisms have been destroyed.
The Bowie-Dick test (for pre-vacuum autoclaves) or Helix test (for hollow loads) verifies steam penetration into the load. HTM 01-05 requires a daily steam penetration test before the first load of the day for Type S and Type B vacuum sterilisers. The test must be performed in an empty autoclave.
A failed Bowie-Dick test indicates a steam penetration problem — it could be a leak, a vacuum pump issue, or a worn gasket. The autoclave must not be used until the problem is resolved.
HTM 01-05 requires an automatic control test for all benchtop sterilisers. Periodic testing — including vacuum leak tests, safety device checks, and steam penetration verification — should be carried out according to the manufacturer's instructions and the practice's maintenance schedule. These tests verify the ongoing mechanical integrity of the autoclave between annual validation visits.
Biological indicators contain spores of Geobacillus stearothermophilus, the micro-organism most resistant to saturated steam. If the sterilisation cycle destroys them, it will destroy any other micro-organism.
HTM 01-05 recommends regular biological controls as part of the overall sterilisation assurance programme. Best practice frequency: weekly as a minimum, after every new installation or autoclave repair, and whenever there is any doubt about the equipment's performance.
HTM 01-05 requires process indicators on every pouch. Class 1 tape does not guarantee sterilisation — it merely indicates that the pouch has been through the autoclave. Chemical integrators (Class 4, 5, or 6) provide more thorough verification by measuring exposure to temperature, pressure, and time.
The Class 6 chemical integrator is the most reliable chemical indicator: it only changes colour when all critical cycle parameters have been reached.
Every biological and physico-chemical control must be documented: date, type of test, result (pass/fail), and any corrective action taken. HTM 01-05 requires every machine to have its own dedicated logbook, and these control records are an integral part of it. They must be accessible during a CQC, HIW, HIS, or RQIA inspection.
Digital traceability allows control results to be archived automatically and linked to the relevant sterilisation cycles, eliminating the risk of loss or oversight. For more details on use-by dates, see the dedicated guide.
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