The screening ịwụ nwere ike etipịa eke nkume ihe dị ka granite, marble na basalt, ihe owuwu ihe mkpofu dị ka brik na ciment, na ndị ọzọ inert ihe dị ka asphalt, slag, poselin ibe, ogbugbo, gypsum osisi, wdg The mwepu urughuru size nke Enwere ike ịgbanwe bọket nyocha site n'ịgbanwe ihe mkpuchi, nke nwere ike izute ihe dị iche iche chọrọ ịkụpịa.