High-pressure steam sterilization is a commonly used sterilization method in biological experiments. According to the different capacity, it can be divided into three types: portable, vertical, and horizontal. Autoclave sterilizers are widely used in the sterilization of equipment, dressings, utensils, liquid medicine, culture medium and other items in institutions of higher learning, medical and health, food chemical industry, and biological research.
 
So, what should be paid attention to in use? What are the factors that affect the sterilization effect? 
1. The sterilization temperature should be a temperature range, not a fixed value. Generally, the high-pressure steam sterilization temperature is a fixed value. For example, the sterilization requirements for test tube slope culture medium and shake flask liquid culture medium are 121℃, 20min , but 121°C is only the lower limit of the sterilization temperature, and the actual sterilization temperature fluctuates between 121°C and 124°C (or 123°C). If it is an automatic temperature control type sterilizer, after setting the lower limit of the sterilization temperature to 121°C, when the temperature rises to 124°C (or 123°C), it will automatically cut off the power and stop heating. When the temperature drops to 121°C, it will automatically start heating. If it is a manual temperature-controlled sterilizer, when the temperature rises to 124°C, manually cut off the power to stop heating, and when the temperature drops to 121°C, manually turn on the power to start heating.
 
2. Different types of autoclave sterilizers have different requirements for the discharge of cold air
1) Non-automatic temperature control sterilizers are mostly small sterilization pots. For this type of sterilizers, cold air must be drained. If the cold air is not drained, it will contribute to the working pressure of the pressure pot after thermal expansion. There is no one-to-one correspondence with the temperature. The displayed temperature is higher than the actual working temperature in the pot. The working temperature of the sterilizer  cannot reach the set sterilization temperature, which will affect the sterilization effect.
2) Automatic temperature control type sterilizers monitor the temperature change in the pot through the thermosensitive electrode, and the temperature displayed on the screen is the actual working temperature in the pot. When the cold air is not completely drained, It can also ensure the temperature requirements for sterilization. Since saturated steam has the best sterilization effect, when using an automatic temperature-control sterilizer, cold air should also be discharged to improve the sterilization effect. There is usually a drain valve under the pot to drain the water, during sterilization, rotate the valve to the left (to the right for draining) to allow a small amount of steam to be discharged. Some sterilization equipment is equipped with an adjustable exhaust valve. During sterilization, the exhaust valve is always kept slightly open to discharge the cold air.
 
3. Factors affecting the sterilization effect
1) Water: Too high water temperature may cause the predetermined vacuum level to change, and the water temperature should be as low as possible. The water used in the sterilization pot should meet the quality of the application water, and the temperature should not exceed 15°C. The hardness value of water is between 0.7～2.0mmoL/L. Hardness values outside this range may cause problems such as scale and corrosion, which will shorten the service life of the sterilization pot. The water used needs to be filtered and processed, and the pot should be kept clean.
2) The degree of dryness of steam: The sterilization pot should use saturated steam with a degree of dryness of not less than 0.9, that is, the moisture content of the steam is not more than 10%, and the degree of dryness is not less than 0.95 under metal loading to keep the temperature and pressure in line with the linear relationship.
3) Sterilization time: Sterilization time refers to the time required for sterilization after the sterilization chamber reaches the specified temperature during the sterilization process. During operation, pay attention to the steam inlet speed and pressure, and generally keep the pressure and temperature rising simultaneously.
 
In order to ensure the safe and effective work of the autoclave sterilizer, the daily maintenance should be strengthened, and various control valves should be tested regularly to ensure its normal working status.