Abstract: An air cleaning machine to be used in houses, offices and so on utilizes an ultraviolet-ray sensor and a gas sensor jointly to combine the characteristics, so that the operation of the appliance becomes extremely smooth. The appliance operates almost immediately especially when a signal from a light is received. If a cigarette is lighted, for example, indoors, the air cleaning machine operates immediately to clean the air, so that the user may actually feel it. When the gas occurs even under the circumstance where the ultraviolet ray does not reach the light sensor, the normal operation is performed, thus allowing the automatic operation to be effected. Accordingly, clean air is normally provided under the optimum circumstance.

Abstract: This invention relates to a sheathed resistance heater which comprises a metal pipe (3), a heating wire (2) received in the metal pipe, and an electrically insulating powder (4) filled in the pipe and also to a method for fabricating same. The electrically insulating powder (4) contains 0.1-10 wt % of the specific type of an oxide by which the heater has a prolonged life because the oxide serves to suppress the metallic component of the heating wire (2) from evaporating, and its insulation resistance under self-heating conditions can be prevented from lowering. The heater has wide utility in both domestic and industrial fields.

Abstract: This invention relates to a sheathed resistance heater which comprises a heating wire (2) received in a metallic pipe 3 and electrically insulating powder (4) packed in the pipe. A metallic powder of the specific type is added to the electrically insulating powder (4), by which the heating wire (2) has a prolonged life by suppressing metal components in the wire from evaporating, the heater being widely applicable for domestic and industrial purposes.