In the fermentation industry production process, the quality of sterile air is crucial. It not only directly affects the output and quality of the fermentation product, but also affects the stability and efficiency of the production process.

1. Pressure of compressed air 

Generally, the air pressure at the outlet of the air compressor is required to be controlled at 0.2~0.35MPa (gauge pressure). In this range, the operating pressure can be guaranteed, which reduces the energy consumption cost compared to high-pressure air compressors. There is no need to force the air pressure at the outlet of the compressor to be too high.This range can not only meet production needs, but also avoid excessive air pressure at the compressor outlet, thereby saving electricity and reducing production costs. 

2. Air flow 

Determine the flow rate of compressed air to be provided based on the overall fermentation tank volume of the fermentation plant or fermentation workshop.The air flow rate is usually calculated by the pilot ventilation ratio or VVM. VVM means the volume (m3) of air introduced into the culture medium under standard conditions per unit time (min) per unit volume (m3). 

3. Air temperature 

In order to reduce the relative humidity of the air, the method of appropriately heating the compressed air before entering the tank is often adopted. Generally, the temperature of the compressed air entering the fermentation tank is controlled to be about 10°C higher than the fermentation temperature.At present, many have cancelled the heating treatment of air before entering the tank, and the air is directly taken in after dehumidification by the cold dryer. 

4. Relative humidity 

Since the filter medium of the fermentation plant's main air filter is currently made of polytetrafluoroethylene, the filtering effect of these filter media will be greatly reduced when they are damp. Therefore, the relative humidity of the compressed air entering the main filter is controlled at 60%~70%. 

5. Cleanliness 

The "sterile air" referred to in the fermentation industry refers to the clean air in which the bacteria content in the compressed air is reduced to zero or reaches the cleanliness level of 100 after sterilization treatment, which can meet the requirements of the fermentation industry. 

The Class 100 air standard indicates that the concentration of particles with a diameter of ≥0.5 μm in the air is directly named as 100 pc/ft3, that is, the number of particles with a diameter of ≥0.5 μm in every cubic foot of air is 100.