The laboratory ventilation system is one of the largest and most influential systems in the entire laboratory design and construction process. Whether the ventilation system is perfect or not will directly have an important impact on the laboratory environment, the health of experimenters, and the operation and maintenance of experimental equipment. Problems such as excessive negative pressure in the laboratory, gas leakage in the fume hood, and laboratory noise have always been difficult problems for laboratory staff. These problems have caused serious physical and psychological harm to the personnel who have been working in the laboratory for a long time, and even the management and logistics personnel working around the laboratory. A scientific and reasonable ventilation system requires good ventilation effect, low noise, easy operation, energy saving, and even requires indoor pressure difference and temperature and humidity to maintain human comfort. Therefore, in the design of the ventilation system, there will be many points that need attention:

1. The fresh air system is adopted for the ventilation of the laboratory, and the exhaust of the fume hood is not circulated indoors. Because the laboratory requires the room to be at negative pressure relative to other auxiliary areas. Therefore, the fresh air volume of the laboratory is designed to be 70%-80% of the exhaust air volume. In addition, 20%-30% of fresh air is sent to laboratory auxiliary rooms, offices, management rooms, inner corridors, etc., and then supplemented to the rooms through the gaps in doors and windows.

2. The laboratory selects a certain number of fume hoods according to the process requirements and functional layout, and some also have some local exhaust hoods. Usually the number of air changes after checking is far greater than 10 times, generally more than 20-30 times, which meets the requirements for the number of air changes. However, the number of air changes is calculated according to the maximum opening area of ​​the fume hood. Data and experience show that 100 fume hoods are only used by 18 or less people 99% of the time. Therefore, the ventilation volume and the number of air changes at the minimum opening area of ​​the fume hood should also be checked. If it is less than the requirements for the number of air changes, an integrated exhaust system should be added.

3. The air volume balance of the fume hood can adopt a constant air volume control system, that is, the exhaust air volume is constant, the air supply volume and the supplementary air volume of the door and window gaps are constant. This method is suitable for laboratories where the maximum exhaust air volume meets the minimum air change requirements.

4. For rooms where the exhaust air volume is much greater than the minimum ventilation volume requirement, a two-stage ventilation control system can also be used to ensure the air volume balance, that is, according to the displacement signal of the fume hood, the exhaust fan and the supply fan have two air supply conditions, and the low air volume operation The condition is applied to maintain the minimum air change requirements and save energy consumption. In this case, the Drug Control Institute adopted a variable air volume control system. When the air volume of the fume hood changes, the exhaust air volume will also be relatively small. At this time, the exhaust fan placed on the roof is required to change frequency with the position of the fume hood cabinet door to reduce the air volume and ensure the constant wind speed of the fume hood. At the same time, the automatic control system changes the frequency of the fresh air fan, reduces the air volume, and maintains the negative pressure balance. Variable air volume system can reduce system energy consumption. If the maximum and minimum air change times of the system are close to each other, the constant air volume system should be considered, which makes the system simple and reduces the initial investment.