A vent or range hood is an exhaust system installed over a stove or other cooking appliance for the purpose of venting smoke, fumes, grease and combustion products out of the kitchen. They typically include exhaust fans and grease traps to catch airborne particles.
An oven can produce a wide variety of potentially troublesome gases. Smoke is a common byproduct of high-temperature cooking, and frying often produces aerosolized grease particles that can stick to cabinets and walls. Steam from boiling can cause condensation on surfaces, and overheating non-stick cookware can produce potentially toxic fumes that can harm family pets. A vent hood helps remove all these from the cooking area before problems arise.
Vent hoods may exhaust to the outdoors, or they may recirculate the air back into the home. The latter style of vent hood usually contains filters to clean the air and activated charcoal to help remove odors and smoke. While the fans in a vent hood do a reasonable job of drawing air into the exhaust vent, opening a door or window to allow fresh air into the kitchen greatly improves the hood's ability to remove odors and gases.
Commercial vent hoods often include fire suppression systems, ensuring that grease fires can be put out quickly before smoke and fumes overcome anyone in the kitchen.