Ventilation building codes establish the minimum rate possible to ventilate the air, keeping indoor air quality acceptable for people. The goal is to prevent people from experiencing adverse effects from poor quality indoor air. As smoke or steam rise from a cook top, proper ventilation should capture the smoke or steam and replace it with cleaner air, usually from outside the building.
Most indoor air quality codes are imposed on commercial buildings, especially those in the food industry that constantly use kitchen cooktops. Poor ventilation increases the chances of a fire and affects the indoor air quality on a greater scale than in a residential situation. Building codes typically categorize cooking appliances as light, medium, heavy or extra-heavy duty. The classification varies by the amount of grease and smoke the appliance emits. Open flames and fryers create more grease and smoke than a pressure cooker. A gas open burner is classified as heavy duty, while an electric cook top is medium duty. Most building codes specify an exhaust hood as an acceptable means of ventilation in a commercial situation, but the configuration and exact requirements may vary based on the business' intended use.
Even if a ventilation system is not required in a home, the building department may still require you to obtain a permit if you install a ventilation system. In cities requiring a ventilation system, an exhaust fan is usually required in the kitchen. The code may specify either a exhaust fan or a ducted ventilation system as appropriate. Either system must conform to a minimum power rate that varies by city, by the location of the range -- against the wall or in an island -- and the width of the hood. The minimum ventilation rate per linear feet may range from as little to 40 CFM to as much as 400 CFM. Building codes may also require protection for the system; the ventilation should extend to the outside of the home, and must be protected from weather, animals and rodents with a screen or other similar material.
Warnings and Tips
Range hoods provide the best ventilation when put close to the cook top. Exhaust systems should discharge outdoors. Recirculating models trap odors and grease in a filters; the filters require regular replacement. Always have the hood sized by a professional who can determine the right size for your cook top. Over-size and high-powered hoods are no more effective than small or lower-powered hoods.