What is a sterilization autoclave?

ABSTRACT

This short article is an introduction to the basic selection of sterilization autoclaves. It defines this type of equipment, summarizes the varieties available and discuss the preliminary problems to cope with in specification and design of sterilization autoclaves.

GENERALS

Both thermal and chemical actions are suitable for sterilization. Thermal sterilization of pharmaceutical
products may be obtained by dry heat or moist heat. A Sterilization Autoclave is a Pressure Vessel intended to perform a Sterilization Process, i.e. the complete inactivation of all viable microorganisms inside pharmaceutical products for human or animal use and / or on the external and internal surfaces of items to be used in health
care or pharmaceutical production environments. Moist-heat sterilization demands for the presence of condensing steam in intimate contact with the microorganisms to be inactivated, at a process temperature generally between 110°C and 140°C. This involves a process pressure between 0.5 bar and 4 bar above the atmospheric pressure at sea level, i.e. between 1.5 abs bar and 5.0 abs bar.

PURE SATURATED STEAM AUTOCLAVES

The level of the process pressure may be dictated one-to-one by the choice of the sterilization temperature. This applies to pure saturated steam sterilization processes, i.e. mainly to sterilization of hard / porous goods: in these processes, the steam fed into the chamber shall both heat the load and sterilize it at the specified conditions.
Pure saturated steam processes are also used for small vials and ampoules filled with solutions to be terminally sterilized. In pure steam sterilization, the intimate contact necessary between condensing steam and the microorganisms to be inactivated demands for the total removal of the air initially surrounding the items to be sterilized.

Nowadays, a vacuum pump connected with the autoclave generally obtains this removal. Next to air removal, pure saturated steam of known, suitable and repeatable quality is fed into the autoclave and the so called “exposure time” begins. Finally, drying and/or cooling phases are performed, to allow a safe extraction of the sterilized items from the autoclave and their conservation under sterile conditions.