The 2009 International Residential Code (IRC) has no general ventilation requirements for residential kitchens. It does list two specific requirements for range hoods, namely that they must discharge outdoors and include a damper to prevent backdrafting, which leaves unaddressed the larger and important subject of what constitutes good ventilation in your kitchen. Kitchens need good overall ventilation, generally provided by the HVAC system (Heating, Ventilation and Air Conditioning System) and additional ventilation above cooking areas. In some cases, a third system may provide auxiliary ventilation for the kitchen.
Overall Residential Ventilation Requirements
The U.S. Environmental Protection Agency used to recommend 15 cubic feet per minute (cfm) of outside air for each building occupant. After the 1973 oil embargo, and as an energy conservation measure, the government called for a reduction to 5 cfm, which proved inadequate and contributed to Sick Building Syndrome as the agency now recognises. They have returned to the 15 cfm recommendation. A 2,000 square foot house generally requires 3 to 5 tons of air conditioning, depending on the climate. The same system circulating outside air only provides at least 15 cfm for 3 to 5 occupants, which in turn provides sufficient general ventilation for the kitchen.
Kitchen Area Ventilation
A house may have adequate ventilation generally, and yet the kitchen still has persistent food odours. Good kitchen ventilation requires a second system to deal with this problem. In the 1970s and 1980s kitchen remodels often featured a recirculating range hood, which hardly ever works well enough to keep the kitchen odour free. If you have one of these or your kitchen does not have a range hood at all, you can install one that vents through an exterior wall. Alternatively, install downdraft range ventilation, which also exhausts air to the building's exterior, often through an underfloor vent. Note, however, that Consumer Reports, in an article rating both conventional and downdraft range ventilation systems, listed two downdraft systems but recommended neither of them.
Other Kitchen Air Systems
For today's larger kitchens, and especially for open-plan kitchen/family rooms, you may need a third ventilation or purification system. One such system, the in-line ventilation system, collects air from the kitchen and other specific areas with additional air-handling requirements, such as the bathroom, and vents it outside through an auxiliary ducting system. You can locate the exhaust fan in the attic. It also helps to buy a low-noise fan, which you can buy at a speciality house that supplies equipment to recording and video post-production houses. One high-end kitchen appliance company has recently introduced an air purification system that comes with its new appliances at no additional cost. It uses ionisation to eliminate odours and airborne bacteria. Other air-ionisers will also work. While these units do not increase kitchen ventilation, but recirculate the air, they will improve air quality.