A mechanical ventilation system uses fans, and sometimes ductwork, to move fresh air through an enclosed parking garage and remove vehicle exhaust such as carbon monoxide and nitrogen dioxide.
Open parking garages ventilate naturally through their wall openings. Garages that fail the openness test, including most below-grade levels, must be ventilated mechanically. The International Mechanical Code sets the required exhaust rate, commonly cited as 0.75 CFM per square foot of floor area, and allows lower rates when sensors confirm the air is clean.
How it works
- Exhaust and supply fans pull contaminated air out and bring fresh air in.
- Jet fans push air across the floor toward exhaust points, replacing much of the ductwork.
- Gas sensors for carbon monoxide and nitrogen dioxide run the fans only as hard as conditions require. See demand-controlled ventilation.
- In larger garages the same fans may also serve smoke control in a fire.
What to watch
- Sensor calibration and replacement, which are easy to neglect and drive both safety and energy use.
- Fan energy, often one of the largest operating costs in an enclosed garage.
- Dead zones where exhaust collects; CFD modeling can find them before construction.
- Fewer combustion vehicles and more EVs reduce exhaust over time, which favors sensor-based control.
The Parkonomics view
Every fan in an enclosed garage is a cost that runs for decades. Design to pass the openness test where the site allows it, and where it does not, let sensors decide when the fans run.
Related terms: Demand-Controlled Ventilation, Cubic Feet per Minute, Openness Calculation, Carbon Monoxide, Enclosed Parking Garage, HVAC