Mechanical ventilation by channel method
The mechanical ventilation system must be independent from other facility systems of the building (except the systems that carry out the normal ventilation of the parking lot) and its capacity should be such that it meets the conditions of paragraphs 2 and 10.
1- The mechanical ventilation system must be designed in such a way that each part includes at least two fans so that if one of the fans fails, the capacity of the remaining fans will not be less than 50% of the required capacity. In addition, the power supply and operation of these systems should be such that the breakdown or failure of one of the fans does not affect the performance of the other fans.
2- The way to control the fans of the compensatory air supply system should be such that the pressure is always negative in both normal conditions and fire conditions.
3- If the fans are located inside the building but outside the evacuation zone, they should be enclosed by structural components with fire resistance equivalent to the same part, and under no circumstances, this resistance should not be less than one hour.
4- Fans and control equipment related to them, if they are likely to be exposed to fire, should have protected cabling so that they are resistant to fire for up to one hour.
5- Setting up the parking lot ventilation system in fire conditions should be possible with both of the following descriptions.
Fire detection and notification system (due to smoke, rapid rate of heat increase, multi-condition flow switch sprinkler detector, etc.)
Switch for fire fighting (manual start)
6- After the fire is detected by the building’s fire alarm system, an order must be immediately issued to change the status of the control panel of the parking lot ventilation system from the normal status to the fire status.
7- The parking lot ventilation system must be designed in such a way that it can be controlled manually and its manual function switch must be placed in a suitable place. This switch should have three positions: off/on/automatic.
8- It should be noted in the design that, whether in the design for the discharge of pollutants or in the design for the discharge of smoke caused by fire, there are no dead spots without ventilation in the entire parking space.
9- The fresh air injection valve should be placed in such a way that it does not lead to the destruction of the smoke layer and the further spread of smoke.
10- The design should be such that the air speed in the escape routes and ramps does not exceed 5 meters per second so that there is no disruption in the escape of the occupants.
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