| 摘要 |
A filter apparatus, particularly for filtering air containing fumes is provided on the inlet side to an exhaust fan (8), electrostatic filters (36) and a flat test filter (38) immediately following the latter. On the outlet side of the exhaust fan (8) a cartridge filter (3) with a plurality of parallel filter cartridges (26) in the flow path is provided. In the flow path directly upstream of the test filter 38, as well as between outlet (14) and the inlet of cartridge filter (3), the pressure is measured by in each case one pressure indicating device (53, 54). When the electrostatic filter (36) becomes saturated, the contamination relatively rapidly increases the flow resistance of test filter (38), which is indicated by a pressure change between the electrostatic filter (36) and the test filter (38). If electrostatic filter (36) is not cleaned, then contamination then increases the flow resistance of cartridge filter (13), which is indicated by a pressure change in the flow path directly upstream of the cartridge filter (3). If there is still no cleaning or replacement of electrostatic filter (36), then the flow resistance becomes higher than the suction force of exhaust fan (8), so that the fact that no further suction is taking place is made immediately apparent.
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