Cubic feet per minute (CFM) is a unit of airflow: the volume of air, in cubic feet, that moves past a point each minute.
In parking, CFM matters mainly in enclosed garages, which must be mechanically ventilated to remove carbon monoxide and other exhaust. The International Mechanical Code sets the required exhaust rate, commonly cited as 0.75 CFM per square foot of floor area, and allows reductions when sensors show air quality is acceptable. Open garages ventilate naturally and generally need no fans. See natural ventilation.
How it is used
- Sizing exhaust and supply fans and ductwork, or jet fans that push air toward exhaust points.
- Calculating fan energy use and operating cost.
- Checking smoke control performance in larger enclosed garages.
Cutting fan energy
- Carbon monoxide and nitrogen dioxide sensors that run fans only when needed. See demand-controlled ventilation.
- Variable-speed fans instead of on and off control.
- Fewer internal combustion vehicles and more EVs reduce exhaust over time. See carbon monoxide.
The Parkonomics view
An enclosed garage running its fans at full speed around the clock is wasting money. Sensor-based ventilation is one of the fastest paybacks available to a garage owner.
Related terms: Demand-Controlled Ventilation, Mechanical Ventilation System, Natural Ventilation, Carbon Monoxide, Computational Fluid Dynamics, Enclosed Parking Garage