The F0 value, also known as the sterilization value or sterilization factor, is a measure of the
sterilization effectiveness of an autoclave. It represents the number of minutes required to
achieve sterilization at a temperature of 121.1°C (250°F), which is the standard temperature
for autoclaving.
Sterilization is generally performed at 121 °C, which is a standard temperature. If we want to
sterilize the material at temperatures other than 121 °C, we must adjust the sterilization time.
F0 values are calculated based on the autoclave’s temperature, pressure, and holding time. A
higher F0 value indicates a more effective sterilization process.
Typical F𝟎 values for autoclaves:
- 8-12 minutes for a standard 121.1°C (250°F) cycle
- 4-6 minutes for a high-temperature 134°C (273°F) cycle
- 20-30 minutes for a low-temperature 115°C (239°F) cycle
F𝟎 values are important in ensuring the sterilization of:
- Medical instruments and equipment
- Pharmaceutical products
- Food and beverages
- Laboratory equipment and supplies
Some materials are heat sensitive and cannot be sterilized at 121 °C. Fo value is used to
determine the exposure time of material for sterilization at a particular temperature. Fo value
is the time in minute for the specified temperature that gives the same thermal lethality as at
121 °C in one minute.
For Example:
If we want to sterilize any material at 115 °C, we have to calculate the Fo value.
Fo= 1 x 10 (115-121/10)
Fo= 1 x 10(-6/10)
Fo= 1 x 10(-0.6)
Fo=3.98 minutes
It shows that that the thermal lethality of 1 minute at 121 °C is equal to the lethality of 3.98
minutes at 115 °C.
Autoclave manufacturers and users often specify minimum F0 values to ensure adequate
sterilization. For example, the Association for the Advancement of Medical Instrumentation
(AAMI) recommends an F0 value of at least 8 minutes for medical instrument sterilization.
F0 = Σ L × dt = Σ 10 (TA-121)/10 × dt
Fo = Equivalent sterilization time (in minutes) at 121°C.
L = Lethal rate
TA = Actual temperature measured.
dt = Time duration (in minutes) between 2 successive
temperature measurements
