The emission rate of fibers released lrorn the new/fresh and used/worn ceramic fiber material. glass wool and man-made mineral fiber material due lo mechanical impact was determined experimentally. The emission rate has been defined as a number or fibers emitted per unit mass and unit impaction energy. The averaged emission rate of short fibers (LS 5 run) for all studied fresh non-asbestos fiber materials ranged lrom 2.2 to 20 fibers/(g·.l), while the emission or long fibers (I,> 5 urn) was between 2.2 and I 00 fibers/(g·J). The susceptibility or worn fiber-containing materials 10 emitting fibrous particles due 10 mechanical impaction was significantly diverse. Emission from glass wool unchanged with the exploitation, while the emission rate of the mineral fiber material increased by a factor of I O·' compared 10 new material. The dominating population or emitted fibers from studied materials ranged trorn 2 10 around 8 pm in length.