Patent ID: 7210536

Claim:
A gas fired hot water heater which is fire-safed against flash-back ignition of fugitive flammable vapors accidentally occurring in the surrounding atmosphere, said heater comprising: (a) a cabinet, (b) a tank located in said cabinet, (c) a combustion chamber in said cabinet, (d) a burner mounted in said combustion chamber for heating water in said tank, (e) a gas-supply line leading into said burner, (f) openings in said cabinet for allowing air to enter said combustion chamber to mix with natural gas and produce a flame in said burner, (g) and nested ellipsoids covering said openings in said cabinet for preventing said flame in said burner from flashing out of said cabinet and igniting fugitive flammable vapors surrounding said cabinet, said ellipsoids being formed from expanded metal sheets made from magnesium alloy foil coated with a corrosion inhibitor.