| 摘要 |
PURPOSE:To prevent the burning of an inhaling passage filter and a drop in the gas permeability thereof by forming a heat resistant protection material laid outside the filter, out of a porous incombustible material having an infinite number of superposed and communicated vent holes, and keeping the average diameter of the holes and the porosity thereof at the specified values. CONSTITUTION:A centrifugal fan 14 rotates, driven by a flat type motor 13, and the fresh air thereby drawn passes a heat resistant protection material 12 and a filter 8. The fresh air is further sent in a radial direction and pushes open an air feed valve 5. Then, the fresh air is supplied from an air feed port 15 to the inside of an enclosure 2 for a user's inhalation. The material 12 is inserted in and coupled to a filter cover 9 so as to conceal the whole of the cross sectional plane of a fresh air flow, at a position outside the filter 8 or the fresh air side thereof. The material 12 is made of a porous incombustible material having an infinite number of superposed and communicated vent holes. Also, the average diameter of the holes is taken at 1.0mm or less, and the porosity thereof is made equal to or above 60%. |
