Abstract: A gas hob has a glass ceramic top plate and gas fired heat radiating burner units below the top plate. Each burner unit has a lower plate which includes a number of concentric chambers. A ceramic burner plate is disposed over the lower plate. The burner plate is perforated to match the arrangement of concentric chambers to provide concentric gas burning rings. The supply of gas to the burner units is controllable by respective control valves enabling gas to be supplied only to the burner plate perforation at which supply of heat is required. A fan below the level of the burner units supplies air to a plenum chamber which communicates with ducts leading to the concentric chambers. The fan supplies combustion air at all times when a burner unit is in operation. Gas from the control valve mixes in the ducts with air from the plenum chamber before entering one of the concentric chambers and the gas burning ring.