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Design of Exhaust and Smoke Exhaust System for Clean Rooms
2025/5/8
The production process of various electronic products will inevitably release all kinds of dust, harmful gases and substances. An effective way to prevent them from spreading and contaminating in the clean room is to adopt local exhaust ventilation at the relevant equipment, and after treatment to meet the standards, discharge them outdoors.
The exhaust system should be independently set up for the following situations: 1) The mixture of exhaust air media can produce intensified corrosiveness, toxicity, and the risk of combustion and explosion; 2) There is a significant difference in toxicity between toxic and non-toxic exhaust media. 3) Flammable, explosive and general exhaust; 4) When designing the exhaust system of a cleanroom, the following technical measures should be taken.
To prevent the backflow of outdoor air into the room, causing pollution and dust accumulation, common anti-backflow measures are as follows: 1) Install medium-efficiency filters; 2) Check valves are adopted, which are convenient to use but have relatively poor sealing performance. 3) It adopts a sealed valve with good sealing performance, but the structure is complex. 4) Adopt automatic control devices, etc. Local exhaust systems containing flammable and explosive substances should adopt fire prevention and explosion prevention measures that are commensurate with the discharged substances. When the concentration and emission volume of harmful substances in the exhaust medium exceed the national or regional regulations on the concentration and emission volume of harmful substances, harmless treatment should be carried out. Only after meeting the standards can it be discharged into the atmosphere. For exhaust systems containing water vapor and condensing substances, slopes and discharge outlets should be provided to promptly remove the condensate.
Ventilation measures should be taken in production auxiliary rooms such as shoe-changing rooms, outerwear storage rooms, washrooms, toilets and bathing rooms in clean workshops. The static pressure values inside these rooms should be lower than those in clean areas.
Cleanrooms should be equipped with emergency exhaust systems in accordance with the requirements of the production process. The accident exhaust system should be equipped with automatic and manual control switches. The manual control switches should be respectively located in the clean room and at convenient operation locations outside the clean room. Generally, for clean rooms (areas) that may emit harmful gases or flammable and explosive gases, emergency exhaust devices should be installed.
The manufacturing materials, insulation materials and coatings of the equipment, pipelines and accessories of the exhaust system should be selected based on the nature and state of the discharged gas, and generally should meet the following requirements.
The air ducts of the exhaust system should be made of non-combustible materials. The non-combustible materials referred to here are various types of metal sheets, including carbon steel, stainless steel, and non-ferrous metal sheets. The selection should be determined based on the nature of the exhaust gas.
2) The air ducts for discharging corrosive gases should be made of corrosion-resistant and hard-to-burn materials. The refractory materials referred to here mainly include fiberglass reinforced plastics and others with an oxygen index equal to or greater than 32.
3) Accessories, insulation materials, sound-absorbing materials and coatings, etc. are all made of non-combustible or flame-retardant materials. The non-combustible materials referred to here mainly include rock wool, glass wool, etc. Flame-retardant materials mainly include rubber and plastic sponges with an oxygen index of 32 or more, polyurethane, etc.
Ii. Smoke Prevention and Exhaust Design for Clean Rooms
A clean workshop is a closed room without Windows or with fixed Windows. Installing a smoke prevention and exhaust system is one of the necessary methods to ensure the evacuation of personnel. Article 6.5.7 of the "Code for Design of Clean Rooms" (GB50073-2001) stipulates that mechanical smoke prevention and exhaust facilities should be installed in the evacuation corridors of clean rooms. The following is an excerpt of the relevant provisions from the draft revision of the "Code for Fire Protection Design of Buildings" for your reference.
1) The determination of smoke exhaust volume: For places equipped with mechanical smoke exhaust facilities, the smoke exhaust volume of the smoke exhaust fan should be no less than 60m ³ /h/m ² when it is responsible for the smoke exhaust of a smoke prevention area. When undertaking a smoke exhaust system with two or more smoke prevention zones, the smoke exhaust volume should be calculated based on the area of the largest smoke prevention zone not being less than 120m ³ /h/m ². The minimum smoke exhaust volume of a single smoke exhaust fan should not be less than 7200 m ³ /h. The selection of smoke exhaust fans: Smoke exhaust fans can use centrifugal fans or dedicated smoke exhaust fans. The air volume should take into account a leakage of 10% to 20%, and the air pressure should meet the requirements of the most unfavorable loop of the smoke exhaust system. On the main pipe at the fan inlet, a fire damper that can automatically close when the flue gas temperature exceeds 280℃ should be installed, and it should be interlocked with the smoke exhaust fan.
2) The setting of smoke exhaust outlets: Smoke exhaust outlets or smoke exhaust valves should be installed on the wall inside the ceiling, and the horizontal distance between them and the adjacent edge of the safety exit should not be less than 1.5m, and the distance from flammable objects should not be less than 1.0m. The smoke exhaust outlet or smoke exhaust valve should be closed at all times, and a manual or automatic opening device should be installed. The farthest horizontal distance between the smoke exhaust outlet and the smoke prevention zone should not exceed 300 meters.
