Emergency exhaust fans are mandatory in catering kitchens. According to "Code for Design of Town Gas" 11.5.3, when commercial gas equipment is installed in basement, semi-basement or enclosed room on the ground, an independent mechanical air supply and exhaust system should be installed; Ventilation should meet the following requirements: normal operation, air exchange times not less than 6 times /h, and emergency exhaust air exchange times not less than 12 times/h; When not working, the air exchange times shall not be less than 3 times/h.

the exhaust air volume of emergency ventilation should be determined by calculation according to the process design requirements, but the air exchange times should not be less than 1.2 times/h. The accident exhaust air volume can be shared by the designed exhaust system in the room and the special emergency ventilation system.

emergency ventilation's air intake should be set in the place where toxic gas or dangerous substances of combustion and explosion may be emitted or gathered the most, and diversion measures should be taken for the dead angle of accident exhaust.

The air outlet of emergency ventilation should try to avoid places where people often stay or pass, and the horizontal distance from the air inlet of mechanical air supply system should not be less than 21m；; When the horizontal distance is less than 21m, the air outlet must be higher than the air inlet and not less than 6m. If combustible gas or steam is excluded, the air outlet should be more than 21m away from the place where sparks may be splashed.

emergency ventilation's fans can be centrifugal or axial, and their switches should be distributed in indoor and outdoor locations for easy operation. If conditions permit, axial fans can also be directly installed on walls or windows. Explosion-proof fans should be selected for fans that emit dangerous gases of combustion and explosion.

emergency ventilation is only used in an emergency, so it can be directly discharged to the outside without purification treatment, and there is no need to set up a mechanical air supply system, and air can be naturally supplied through doors and windows, but attention should be paid to leaving channels for natural air supply.

Extended information:

The design of emergency exhaust fan should meet the following requirements:

1. Auxiliary production workshops such as high-voltage switchgear room, capacitor room, oxygen and acetylene cylinder warehouse, charging room of automobile maintenance room, battery repair room, fuel injection pump room, fuel accessory room and painting room should be provided with emergency exhaust devices and emergency exhaust.

2. The emergency exhaust fan should be equipped with switches in indoor and outdoor locations which are convenient for operation.

3. The accident exhaust fan should be located at the place with the largest emission of harmful gas or explosive dangerous substances, and measures should be taken to prevent short circuit of airflow.

4. Eliminate the local exhaust system with explosive substances, and the motor of the ventilator should be explosion-proof.

5. The cable tunnel shall be provided with emergency exhaust air, which shall be calculated according to the wind speed of tunnel section of 1.5 ~ 1.7m/s, and natural air supply shall be adopted. The heights of air inlet and air outlet shall be not less than 2m and 2.5m respectively from the outdoor floor.

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