Ventilation Airflow in F300 Car Park Smoke Exhaust Design

Make-up air (fresh air) is the amount of outdoor air that is mechanically introduced into the parking area to replace the air being exhausted. The fans used to supply this fresh, uncontaminated air into the space are referred to as make-up air fans (supply fans).

According to the Iranian Fire Department regulations (2015 edition), a minimum of 6 air changes per hour must be provided for all parking levels under normal conditions to dilute vehicle exhaust gases and reduce pollutant concentrations. In the event of a fire, at least 10 air changes per hour must be provided for the affected floor to effectively extract smoke and combustion products. The make-up air volume should be 50‑75% of the exhaust air volume, and the parking area must be maintained under negative pressure at all times.

The mechanical ventilation system must be designed so that each zone is served by at least two fans. In the event that one fan fails, the remaining fans must still be capable of delivering no less than 50% of the required capacity. Furthermore, the power supply and control arrangements must ensure that the failure or shutdown of one fan does not affect the operation of the others.

As a real‑world example of calculating the required smoke exhaust airflow and make‑up air volume in F300 car park smoke exhaust system design, the Lotus Hotel project—designed and executed by our company—is presented below.

As previously mentioned, the ventilation air volume for each zone is based on 6 air changes per hour under normal conditions and at least 10 air changes per hour during a fire. The fresh air volume in both normal and fire modes is considered to be 60% of the total ventilation and smoke exhaust air volume. The table below shows the ventilation and smoke exhaust airflow volumes for each zone.