High-pressure steam sterilizer belongs to moist heat sterilization. Due to the potential of moist heat sterilization, the temperature of the sterilized items is lower than that of the steam, and the steam condenses into water on its surface, releasing the potential, which can quickly increase the temperature of the sterilized items.

Compared with dry heat sterilization, water and steam have higher heat capacity, faster heat conduction and stronger penetration than air, so sterilization requires lower temperature and shorter time. Therefore, the temperature rise should not be too fast. The sterilization time is calculated based on the duration after the required temperature is reached, but the temperature rise and fall process also plays a role in sterilization. If the temperature rises and falls too quickly, it will affect the total accumulated temperature and thus the sterilization effect of the autoclave. In addition, if the temperature rises too quickly, especially when using external steam, the temperature rise inside the sterilized item will lag behind the indicated temperature of the pressure gauge.

Pressure steam sterilizers can be divided into two categories: bottom exhaust type and pre-vacuum type. The bottom exhaust type relies on the principle of displacement due to the difference in specific gravity and temperature between steam and air. The water vapor entering the sterilizer discharges the cold air from the exhaust pipe at the bottom. There are three common types: portable, vertical and horizontal.