Pre-heating Phase: Cycle starts with recirculation of water in closed-loop from the water sump through a heat exchanger and to the chamber. During recirculation, the water gets heated while passing through aheat exchanger. The heated water raises the temperature and pressure within the load and attains the sterilization temperature. External air is gradually purged in the chamber(based on the load-temperature)to balance the pressure across the container wall.

Sterilization Phase: On attaining sterilization temperature, the sterilizer holds (maintains) the temperature and pressure of the chamber till predefined time. Usually, it is 121 degrees C and time of 30 minutes (considering the overkill approach) for super-heated water spray sterilization. The pressure across the wall of the container is continuously balanced by regulating the air purging in the chamber.

Exhaust Phase: After the sterilization phase, the chamber temperature is reduced by cooling the recirculation water through a heat exchanger. With a reduction in the load temperature, the pressure inside the container also reduces. This reduced pressure inside the container can too create a pressure imbalance across the wall of the container and damage the load. Therefore, to avoid such damages, the external air pressure is gradually reduced by monitoring the load temperature during exhaust. Once the chamber temperature reaches the desired value, the chamber pressure is released, and the load is ready for unloading from the chamber.

Rapid Cooling Cycle:

As the name indicates, a rapid cooling cycle is employed to cool down the load instantaneously after the sterilization phase. At the end of a standard sterilization cycle, the load is generally hot; so, while unloading, safety precautions are necessary. After unloading, the load is kept idle till it cools down for further usage. Hence, additional safety measures (using PPE) and the extra wait time is necessary after completion of a standard sterilization cycle.
With Rapid cooling cycle, both the concerns, i.e. safe handling and wait time, are eliminated, so the load can be used immediately after unloading from the sterilizer. In the rapid cooling cycle, during the cooling phase, cold water enters the jacket or chamber to speed up the cooling process. There are two types of rapid cooling cycles available, i.e. Direct (Spray) cooling and Indirect (Jacket) cooling.

Direct(Spray) cooling cycle

The Super-heated water spray cycle is the fastestand economical method for achieving terminal sterilization. The sterilization is attained using super-heated water instead of saturated steam. The products are sterilized at an elevated pressure relative to temperature in this method.Here, the super-heated water is circulated in a closed loop through the chamber to sterilize the product. As the load temperature increases, additional sterile compressed air is purged in the chamber to balance the pressure across the wall of the container.

Indirect (Jacket) Cooling Cycle

In Jacket cooling cycle, after the sterilization is complete, the cold water is circulated in the chamber jacket until the desired load temperature is achieved. This cooling method is suitable for the load such as laboratory glassware, open glass containers or the load that cannot be wet when unloaded from the chamber. An additional advantage of using the jacket cooling cycle is that the cooling can be achieved through normal water and need not be sterile water.

Purge Phase: During the Purge phase, the steam enters the sterilizer chamber and displaces the air within the chamber through a chamber drain port. The temperature and pressure of the chamber gradually increase and attains the sterilization temperature.

Sterilization Phase: On attaining sterilization temperature, the sterilizer holds (maintains) the temperature and pressure of the chamber till predefined time. Usually, it is 121 deg C for 20 minutes (considering the overkill approach) for steam sterilization.

Cooling Phase: Once the sterilization hold time is over, the cooling water is circulated, either through a jacket or by direct spraying. The cooling phase will continue until the desired temperature is attained.

Exhaust Phase: After the cooling phase is over, the chamber exhausts the pressure, and the sterilized material is ready for unloading from the chamber.

Flash Cycle

Flash cycle is commonly used in the healthcare industry for quick sterilization of the load. The flash cycle typically finds its application in small capacity autoclaves used in dental clinics or the operation theatres. Here, the cycle time varies from 3 to 10 minutes with the sterilization temperature ranging from 132 to 135-degree centigrade. The flash cycle is performed as gravity cycles at higher sterilization temperature and shorter cycle time. This sterilization method is generally used for the instruments required in an emergency procedure. Flash cycle is recommended only for validated load/instruments and not for the material such as implants, single-use items and other material that is not validated.

Heat-up: During the Heat-up phase, the steam enters the sterilizer chamber and displaces the air within the chamber through a chamber drain port. The temperature and pressure of the chamber gradually increase and attains the sterilization temperature.

Sterilization Phase/Hold: On attaining sterilization temperature, the sterilizer holds (maintains) the temperature and pressure of the chamber till predefined time. Usually, it is 132 to 135 deg C for 3 to 10 minutes for steam sterilization.es C and time of 20 to 30 minutes (considering the overkill approach) for steam-air mixture sterilization.The pressure across the wall of the container is balanced by regulating the air purging in the chamber.

Cooling Phase: After the sterilization hold time is over, the load is allowed to cool until the desired temperature is attained. Once the load is cooled to the desired temperature, the sterilized material is ready for unloading from the chamber.