The results of many days experiments in Chornobyl at flowing of atmospheric aerosol through many layers Petrjanov's filter materials at linear speed 0.80 - 0.85 and 1.60 - 1.70 m/s are presented. It was received, that a pressure drop of the first layers from materials ФПА-70-0,10 and ФПА-70-0,16 certainly are increased. A pressure drop of the second layers from materials ФПА-70-0,23 and ФПА-70-0,28 also are increased, but slower then for the first layers. A pressure drop of the last layers from materials ФПП-15-1,9 and ФПП-15-3,0 practically not change. It is follow, that materials ФПА-70-0,2 and ФПП-70-0,2 may be used as forefilter of high efficient materials ФПП-15-1,5 and ФПА-15-2,0.
Keywords: Chornobyl zone, fibre filters, many layers compositions, atmospheric aerosol, water fume, flow speed, pressure drop, coarse fibre forefilter.