remote control, motorized height adjustment, thermal sensor, overheat protection, boost mode, delayed shut-off, filter cleaning reminder, active noise cancellation, temperature display, user presets (memory), and so on. Extractor hoods may be made from a variety of materials, including stainless steel, copper, bronze, nickel silver, zinc, tempered glass, wood, aluminum, brass, heat-resistant plastics, and more. NFPA 96 Standard for Ventilation Control and Fire Protection of Commercial Cooking says that mesh filters shall not be used. It requires that "Listed" grease filters shall be tested in accordance with UL 1046, Standard for Grease Filters for Exhaust Ducts. Types Kitchen hoods are broadly classified into ducted hoods and ductless hoods. This classification of these kitchen hoods is done purely on the basis of how the hoods process the air that is being sucked in. Ducted kitchen hoods Ducted kitchen hoods are the most common and a primary type of kitchen hood. As the name suggests, a ducted kitchen hood has a duct that is used to process and expel any smoke that is generated on top of the kitchen hob. Large sized duct hoods are widely used not just in homes but also in commercial restaurants and communal kitchens too. Ductless kitchen hoods Ductless kitchen hoods do not have a duct that is used to process the air. Instead, it makes use of strong air filtration and then pumps out the air back into the room. These types of range hoods are usually used in houses. Filters Filters remove most odors and particulates, including grease, from the vented air. There are three main types of filter: Mesh or cassette filters are made from aluminium mesh strips placed one over the other. They are highly effective in the capture and removal of oil and grease from smoke of both ducted and ductless chimneys. They must be cleaned regularly. Baffle filters are made of steel/aluminium frames with curved panels. The curves catch on grease, oil and other particulates. They are durable and easy to clean and are used in both ducted and ductless chimneys. They must be cleaned regularly. Charcoal filters are made of fine powdered activated charcoal. They are primarily used for ductless applications. They cannot be cleaned, but need to be replaced regularly. Hood overhang Greater hood overhangs are suggested to help contain cooking fires in the hood area protected by the fire suppression system. Noise levels Loud kitchen hoods can affect well-being,