The pressure losses occuring during filtering air purification from the dust waste arisen during machining of wood materials are subjected to the influence of the moisture contained in the air. The carried out laboratory tests with use of standard version of the polyester unwoven fabric KYS series PROGRESS and the other version of the same fabric with hydrophobic protection of working surface let us claim that the usage of silicone appret is plainly advantageous in conditions of air relative humidity 85%. This advantage manifests itself by general reduction of the resistances of air flow by about 2-5% and increasing of the regeneration ability of the hydrophobic unwoven fabric along with the filtration velocity.

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