Critical to the daily operation of hospitals, dental offices, veterinary clinics and other medical establishments around the world is the supply of sterile instruments and equipment for surgical and medical procedures. For many, autoclaving is routine practice.

There are 6 critical factors essential to achieving sterilization. Unless all of these factors are satisfied, sterilization cannot take place.

1 time

Not all organisms die at the same time. Sterilizing conditions must be maintained within the autoclave chamber for a period of time sufficient to allow all organisms to be killed.

Generally, spores of thermophilic (heat-loving) bacteria such as bacillus stearothermophilus (Bst), a bacterium found widely in soil, ocean sediments, and hot springs, are used as challenge organisms to test sterilization cycles.

2 – Temperature

The heat denatures the bacteria’s proteins by breaking the hydrogen bonds and thus killing the bacteria. Increasing the temperature of the steam inside the autoclave chamber significantly reduces the time required to achieve sterilization.

The temperature of saturated steam is directly related to pressure. That is why autoclaves are pressurized systems. Pressure is not necessary to kill bacteria, but is a product of the temperature required to achieve sterilization conditions.

3 – Humidity

The level of moisture in the steam significantly affects the amount of energy it can store. Saturated steam can store much more energy at a given temperature than dry air or water.

For this reason, superheated steam (which contains less moisture) or steam containing liquid water should be avoided. Good water quality is important to minimize the presence of contaminants in the steam. Tap water should never be used.

4 – Direct contact with steam

In order for steam to transfer its stored energy, it must condense on every surface of the load being sterilized. If direct steam contact does not occur with ALL surfaces, internal and external, sterilization will not take place.

5 – Air removal

The air acts as an insulator around the load surfaces preventing direct contact with the steam. The presence of even a small air bubble on the surface of the load can cause a spot of contamination.

Autoclaves use different air removal methods depending on their type. Gravity displacement autoclaves are the least effective at removing air and are therefore only suitable for sterilizing unwrapped solid instruments. Hollow instruments, wrapped instruments, or porous loads should only be sterilized by dynamic air removal methods.

6 – Drying

Unless the sterilized load is for immediate use, the packs must be dry before removing from the sterilizer. The presence of condensation can cause recontamination.

All of the above factors are critical to the sterilization process. If any of these conditions are not met, sterilization will not be performed.