In the design and construction of the laboratory, the most important thing to pay attention to is the design of the ventilation system. The design of the laboratory air conditioning and ventilation system includes air treatment, cooling, heating and dehumidification, air flow organization, control, and safety. It is a whole instead of Independent system. The primary problem to be solved by the ventilation design of the laboratory is the safety problem, and it is also necessary to consider creating a comfortable working environment for the experimenters, solving the problems of temperature, airflow, and noise, while ensuring low energy consumption, stable system, and easy Control, easy to operate and manage. In short, it is to design from the aspects of safety, comfort, energy saving, and reliable operation.

CEIDI has compiled the relevant knowledge points for the ventilation frequency and the air supply and exhaust system that everyone is most concerned about in the laboratory design and shared with you.

Laboratory air changes

The "Chemical Heating, Ventilation and Air Conditioning Regulation Design Code" stipulates that the minimum air exchange rate of the laboratory room is generally 6 times/h to 8 times/h. ASHRAE stipulates that the overall air change frequency in the laboratory should be determined by the following air volume: the total air volume discharged from the local exhaust equipment or other room exhaust; the cooling air volume required to take away the heat load of the room; the minimum number of air changes required. In use, the minimum number of air changes in the laboratory should be maintained at 6 times/h~10 times/h.

Under normal circumstances >10 times/hour room air changes are considered appropriate. However, when there is a possibility of high thermal load analysis equipment in the laboratory, or a relatively large amount of local exhaust in the room, the ventilation volume may need to be increased accordingly. The wet chemical room has a fume hood, and the heating room has a large number of heating furnaces. The calculation method of the fume hood refers to the "Chemical Heating, Ventilation and Air-Conditioning Design Code" for light, moderate or dangerous hazardous substances. When the indoor ceiling is filled with air, the minimum suction surface of the operation port of the fume hood The speed is 0.5m/s. For the utilization rate of fume hoods, when the number of fume hoods is greater than 2, the simultaneous utilization rate should be 60%~70%. The heating furnace calculates the required exhaust air volume based on the heat balance law that maintains the heating temperature in the furnace. Through the above, the total safe ventilation volume can be calculated. In addition, the air-conditioning volume calculated by the load is compared with the minimum number of air changes 10 times, and the maximum of the three is taken.

Laboratory air supply and exhaust form
The "Chemical Heating, Ventilation and Air Conditioning Regulation Design Code" stipulates that when the exhaust air volume of the laboratory is large, an outdoor fresh air supply system should be installed and the fresh air load should be included.

The "Science Laboratory Building Design Code" stipulates that each exhaust device should be equipped with an independent exhaust system. All exhaust devices in the same laboratory should share an exhaust system. The laboratory that uses the exhaust system continuously during working hours should be equipped with an air supply system, and the air supply volume should be 70% of the exhaust air volume, and the air supply should be air purified according to the process requirements. For heating areas, the supply air should be heated in winter. The supply air flow should not disrupt the normal operation of the laboratory exhaust device.

ASHRAE stipulates that all gases exhausted from the chemical laboratory must be directly discharged outdoors and cannot be recycled. Therefore, unless the chemical laboratory also has cleanliness requirements, it is necessary to maintain its negative pressure relative to the adjacent area. Whether to choose a 100% fresh air supply system should be an important part of the laboratory risk assessment. An independent exhaust system is set up between each unit of the laboratory, and the exhaust is installed on the roof. The wet chemical room and heating room must be treated with fresh air due to the production of toxic, corrosive, and high-temperature gases. For other general laboratory rooms for computer analysis by staff and constant temperature and humidity rooms for material testing, a 100% brand new air supply system is not the only option. Because of the different process functions of the laboratory, fresh air ventilation or fresh air air treatment is not necessary. It can only be the first priority to meet the process. 100% of the fresh air is for the environment of the fume hood, and for the general laboratory circulating air treatment that can meet the requirements, 100% of the fresh air is not necessary. Moreover, in a fresh air-conditioning environment, energy consumption is very high.

The number of air changes is regulated by certain codes, but the codes generally only formulate a range. In actual construction, the understanding of the function of the laboratory is the decisive factor for the selection and design of the ventilation system. CEIDI designers usually study all the factors before designing, such as pollution, chemical gas laboratory ventilation, this is generally to consider the odor generated by the laboratory you operate in the laboratory or other serious effects It can be designed according to the nature; if the laboratory volume is large, the air exchange is relatively large. The smaller the amount of experiment, the smaller the air exchange. This needs to be designed according to the type of laboratory function and the amount of actual operation. For experienced laboratory service providers, this is the idea that their design team will inevitably design.

In addition, according to ASHRAE specifications, laboratory air conditioning and ventilation design parameters include: 1) indoor and outdoor temperature and humidity requirements; 2) air quality; 3) equipment and process heat load, including sensible heat and latent heat; 4) expected increase in internal load; 5) Minimum number of air changes; 6) Air intake and make-up; 7) Exhaust equipment type; 8) Control and alarm; 9) The size and number of fume hoods can be adjusted; 10) Room pressure difference; 11) Equipment and Power backup.