Also called: Dry heat sterilizer, Hot air steriliser, Oven steriliser
Dry Heat Sterilizer: How It Works and When to Use One
Hot-air sterilisation is slower than steam but still has a place. What it suits, what it ruins, and how to run and monitor it properly.
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How dry heat sterilises
Dry heat kills microorganisms by oxidation, which needs much more heat and time than steam — condensing steam releases its heat into the load almost instantly, while hot air is a poor conductor. Without air movement, the load heats slowly and unevenly.
Static (gravity convection)
Air circulates by natural convection only. Cheaper, but slower to heat and with larger temperature differences between shelves.
Forced air (mechanical convection)
A fan moves hot air through the load for faster, more even heating. This is the type to choose for instrument sterilisation.
Rapid heat transfer
Some units use higher temperatures and high-velocity air for much shorter cycles, mainly for unwrapped instruments. Follow the maker’s validated settings exactly.
Temperatures and times
Exposure time starts only when the whole load — not just the air — has reached temperature. Add heat-up and cool-down, and a full dry heat cycle can run for several hours.
| Temperature | Minimum exposure once the load is at temperature |
|---|---|
| 160 °C | 120 minutes |
| 170 °C | 60 minutes |
| 180 °C | 30 minutes |
What suits dry heat — and what does not
| Item | Dry heat? | Why |
|---|---|---|
| Glassware and metal containers | Yes | Heat-stable, and no moisture left behind |
| Sharp or carbon-steel instruments | Yes | No steam to dull edges or cause rust |
| Oils, petroleum jelly and powders | Yes | Steam cannot penetrate them |
| Textiles, gauze and paper wraps | No | Scorch or degrade at these temperatures |
| Plastics, rubber and silicone | No | Melt or deform |
| Water-based liquids | No | Need a steam liquids cycle |
| Dental handpieces | Usually no | Rarely rated for dry heat — check the IFU |
Dry heat vs autoclave
| Dry heat sterilizer | Steam autoclave | |
|---|---|---|
| Typical cycle | 160–180 °C for 30–120 min, plus heat-up and cool-down | 121–134 °C, 3–15 min hold inside a 30–60 min cycle |
| Wrapped and hollow loads | Heats them slowly and unevenly | Yes, with vacuum air removal (Class B) |
| Instrument corrosion | None | Possible with poor water or carbon steel |
| Biological indicator | Bacillus atrophaeus spores | Geobacillus stearothermophilus spores |
| Typical users | Labs, pharma glassware, some dental and beauty settings | GP, dental, surgical, vet and lab |
Read next All steriliser types comparedAutoclave temperature and pressure
Running and monitoring a dry heat sterilizer
- Load loosely with space between items so air can circulate; never stack trays.
- Do not open the door mid-cycle to add items — the exposure time must restart.
- Use wraps, pouches or containers rated for dry heat; ordinary steam pouches may scorch.
- Use chemical indicators designed for dry heat; steam indicators do not respond correctly.
- Run dry heat biological indicators on a regular schedule and after any repair.
- Have temperature accuracy and uniformity checked at each service, and let loads cool before handling.
Glass-bead units and registration
Small glass-bead “sterilisers” heat a cup of beads and only the tip of an instrument, for seconds. They are not a validated method for sterilising instruments. Under the Medical Device Act 2012 (Act 737), a medical device must be registered with the Medical Device Authority (MDA) before it is imported, exported or placed on the Malaysian market. A steriliser sold for reprocessing medical instruments is itself a medical device, so ask for its MDA registration number and check it on the MDA’s public register before you pay.
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Frequently asked questions
What temperature does a dry heat sterilizer use?
Is dry heat better than an autoclave?
Can a kitchen or lab oven be used as a dry heat sterilizer?
Which spore test is used for dry heat?
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