Abstract: A catalyst 1 is provided in a gas passage 4 for communicating between a gas flow-in unit 12 and a gas flow-out unit 13, and the catalyst 1 is heated by a heater 2, and a temperature sensor 3 for detecting the temperature of the heater 2 is provided inside the heater 2. By feeding power to the heater 2, the wall temperature of the heater 2 is raised to heat the catalyst 1, and then malodorous gas containing odor substances is passed in from the gas flow-in unit 12. The malodorous gas passes through the catalyst 1 in the gas passage 4 to be oxidized to be harmless and odorless, and is discharged from the gas flow-out unit 13.

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.