Synopsis: This article discusses options for kitchen ventilation systems, covering standard range hoods and downdraft designs. A sidebar discusses how elbows and other fittings affect the flow of air.

My family once lived in a house in Buffalo, New York, that had no kitchen exhaust system. It wasn’t much of a problem in summer. A stiff breeze off Lake Erie whisked cooking odors, heat and steam out the window. But in winter, when cooking made the house smell like a crowded apartment building, we cranked open foggy kitchen windows and let the arctic winds draw the odors — and the heat — outside.

If you’ve ever lived without kitchen ventilation, having it may seem like a luxury. Kitchen exhaust systems go a long way toward improving air quality throughout a house, however. They suck out odors and heat and get rid of the grease and moisture generated by cooking. They also remove noxious by-products of combustion from natural-gas ranges and some types of indoor grilling. Exhaust systems are invaluable in cooking accidents, too.

There are two types of kitchen ventilation: intermittent and continuous. Range hoods and downdraft ventilators — switched on as needed — are examples of intermittent systems. These types of units move a large amount of kitchen air relative to the second type of system, which is a continuously running whole-house exhaust fan, or multipoint system, sometimes referred to as background ventilation. (A multipoint system is not a heat-recovery ventilator, although multipoint HRVs are available.) A multipoint system typically has a kitchen intake and often contains a device that lets the user turn up its exhaust capabilities during cooking.

There’s lively debate among indoor-air-quality specialists and manufacturers about the amount of ventilation needed in the kitchen and about the best-working systems. Some professionals prefer intermittent fans because of their location…