The main factor affecting the sterilization effect of the pressure steam sterilizer is the cleanliness of the cold air in the sterilization chamber. When there is cold air in the sterilization chamber, the cold air is surrounded by the steam in the sterilization chamber. A cold air mass is formed, and the central part of the cold air mass, because the steam cannot penetrate, conducts heat exchange. Then the temperature of the central part of the cold air mass is often much lower than the temperature of the steam around it, and the temperature of the steam around the cold air mass may have reached 121 ℃ , and the central temperature of the cold air mass may only be more than 20 ° C (this phenomenon is more common in the sterilization of fabric wrapping).

And because the density of cold air is greater than the density of steam, the same volume of cold air must be larger than the same volume of steam. For the sterilization equipment in the cold air mass, due to the barrier of the cold air, it cannot exchange heat with the steam normally, and the normal sterilization temperature cannot be reached. The temperature of the cold air mass rises slowly, and the volume expands gradually; it causes the pressure in the sterilization chamber to increase, which is a typical high pressure and low temperature. Failure to complete sterilization within the specified time will cause the sterilization effect to fail. Therefore, the key to ensuring the sterilization effect is whether the cold air is exhausted.