For commercial kitchens, it is important to check that the amount of return air balances out with the output capacity of the exhaust fan. It is important to replace air that was removed from the kitchen area. Make-up air helps the exhaust system function properly. The exhaust fan must run simultaneously with the exhaust fan. This is obligatory because if only one fan is running and the other is not, hazardous may occur within the ventilation ductwork. This can also result in kitchen fires.

The air that returns back into the building should be within a certain temperature range; this is for safety and comfort. For example, in colder environments air cannot be cooler than 50 degrees Fahrenheit and in warmer climates air must be cooled to room temperature, around 60 degrees Fahrenheit. The integrated system of a commercial kitchen vent hood serves to make a restaurant and its kitchen a safe and comfortable for workers and customers.