PURPOSE: To obtain high relative sensitivity, to facilitate manufacture, and to reduce the price by inserting an acid catalyst net in the inside of the tip of a nozzle, and wrapping an acid catalyst net round the outer peripheral of the tip of the nozzle.
CONSTITUTION: An acid catalyst net (Pt net) 2 is inserted in the inside of the tip of a nozzle N formed by stainless steel material, and a Pt net 4 is wrapped round the outer periphery of the tip 1 of the nozzle N, too. In this arrangement, the heat of hydrogen flame H is easily transmitted to the tip 1 by the net 4, and as the tip 1 of the nozzle N is formed by stainless steel material which has high heat conductivity and heat-resisting property to make the heat capacity smaller, the temperature can be raised efficiently, and the temperature is raised until the Pt net 2 inserted in the inside is activated as a catalyst. According, the need of a ceramic heater can be eliminated, and high relative sensitivity can be obtained.
KOIKE HIDEKI
ISHIMOTO SHUICHI
