Written and maintained by CASRAI Editorial Board
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This page describes products and general use; it is not medical advice.
Short answer: steam autoclaves sterilize at two reference temperatures, 121°C (250°F) in gravity displacement sterilizers and 132–135°C (270–275°F) in prevacuum and pulsing sterilizers. The temperature only counts together with a minimum exposure time, the type of load, and how well air has been removed from the chamber. Who uses this: sterile processing staff, clinic and laboratory technicians, and buyers of autoclave consumables such as pouches and indicator tape.
What temperature does an autoclave sterilize at?
The CDC’s guidance on steam sterilization gives the recognized minimum exposure periods for wrapped healthcare supplies as “30 minutes at 121°C (250°F) in a gravity displacement sterilizer or 4 minutes at 132°C (270°F) in a prevacuum sterilizer.” For flush-pressure pulsing sterilizers it states that “typical sterilization temperatures and times are 132°C to 135°C with 3 to 4 minutes exposure time” for porous loads. The common shorthand “autoclave sterilization temp” therefore means one of these pairings, not a single number. See what an autoclave is for the device itself.
Temperature and minimum time by cycle type
| Sterilizer / cycle | Temperature | Minimum exposure | Load named by the source |
|---|---|---|---|
| Gravity displacement | 121°C (250°F) | 30 minutes | Wrapped healthcare supplies (CDC) |
| Prevacuum (high-speed) | 132°C (270°F) | 4 minutes | Wrapped healthcare supplies (CDC) |
| Steam flush-pressure pulsing | 132–135°C | 3–4 minutes (typical) | Porous loads (CDC) |
| Gravity displacement, 10 lb microbiological waste | 121°C | At least 45 minutes | Microbiological waste (CDC) |
These are recognized minimums for the stated load and sterilizer design, not universal settings. Exposure time varies with the item, whether it is wrapped, and the sterilizer type. The manufacturer Tuttnauer, in its knowledge-center article on autoclave temperature range, describes the same 121°C gravity and 132–134°C pre-vacuum split, and extended cycles of 18 minutes or more at 134°C or higher for prions. That is a manufacturer’s technical page, not an instruction for use, so follow the instructions for your own sterilizer and items. Prion work has its own rules; see prion decontamination protocols.
Why gravity and prevacuum cycles differ
Steam only sterilizes where it reaches the surface of the item. In a gravity displacement sterilizer, steam, being lighter than air, forces air out through the drain vent; the CDC describes this design as used primarily for laboratory media, water, pharmaceutical products, regulated medical waste and nonporous articles whose surfaces have direct steam contact. In a prevacuum sterilizer a vacuum removes air first, giving “nearly instantaneous steam penetration even into porous loads.” Faster air removal is why the prevacuum cycle reaches sterilization in 4 minutes at a higher temperature instead of 30 minutes at 121°C. The 45-minute waste figure shows the same effect from the other side: a dense bag traps air, which slows steam penetration. Compare the cycle designs in gravity, pre-vacuum and liquid cycles and types of autoclaves.
It has to be dry saturated steam
The CDC specifies dry saturated steam with a dryness fraction of 97% or higher. Wet or superheated steam does not do the same job as the temperature on the display suggests.
How temperature is verified
A chamber reading is not proof that a load was sterilized. The CDC points to three checks:
- Biological indicators: spores of Geobacillus stearothermophilus, the organism used for steam cycles. The CDC gives a D-value at 121°C of 1–2 minutes. See autoclave validation with biological and chemical indicators.
- Chemical indicators: placed on the outside and inside of each pack.
- Bowie-Dick test: for prevacuum sterilizers, run at 134°C for 3.5 minutes, daily before the first processed load, to detect air removal failures.
The idea of a probability target for sterility is covered under sterility assurance level.
Safe use and handling basics
Use cycle settings from the sterilizer and item instructions, and match the cycle to the load. Not every material tolerates 121°C; check which plastics are autoclavable before loading. Supplies that arrive in sterile packaging, such as medical bandages, are single-use and are not put through a steam sterilizer; this page covers reusable items.
Common mistakes
- Quoting “121°C for 15 minutes” without the load, wrapping and sterilizer type. The CDC minimum for wrapped supplies in a gravity unit is 30 minutes.
- Using the prevacuum 4-minute figure on a gravity sterilizer.
- Treating the displayed temperature as the verification. Indicators are the check.
- Cutting exposure time for dense or bagged waste, where the CDC cites at least 45 minutes at 121°C.
Frequently asked questions
What is the standard autoclave sterilization temperature?
121°C (250°F) for gravity displacement sterilizers and 132–135°C for prevacuum and pulsing sterilizers, each with a minimum exposure time.
How long must wrapped supplies stay at temperature?
The CDC lists 30 minutes at 121°C in a gravity sterilizer or 4 minutes at 132°C in a prevacuum sterilizer.
Is “autoclave sterilization temp” a different number?
No. It is the same question; the answer is the cycle table above.
Sources
- CDC, Steam Sterilization, Disinfection and Sterilization Guidelines (page dated November 28, 2023), checked 2026-10-29.
- Tuttnauer Knowledge Center, Autoclave Temperature Range for Effective Sterilization, manufacturer article, checked 2026-10-29.
