HEATER

PURPOSE:To enable the feed of secondary air to the central part of flame by a method wherein the burner port of a burner head to burn fuel-air premixture of gaseous fuel and combustion primary air is formed approximately in a U-shape. CONSTITUTION:Gaseous fuel is premixed in a vaporizing mixing chamber 13 with primary air by means of an agitating plate 14, and injected for ignition through small circular holes 23 of a burner port part 24 of a burner head 22 after the passage of it through a throttle port 18 and through-holes 20. Flame F is formed above a burner port part 24 for blue flame combustion. Since the burner port part 24 of the burner head 22 is formed approximately in a U-shape, flame F extending in a cylindrical shape toward above is formed to the burner port part 24, and a non-flame space X having a specified width is formed to a part of a peripheral direction. Since the central part of the flame F is brought into a negative pressure state through a draft action occasioned by the rise of combustion gas, secondary air is sucked and fed to the central part of the flame F from the non0flame space X. Thus, secondary air can be fed to the central part of the flame through natural ventilation produced by the draft action of the flame F, and the generation of CO can be suppressed as the generation of combustion noise is reduced.