Polymeric raw material passing through the extrusion machine and other forming devices undergoes the processes of destruction, which result in the formation of potentially harmful substances and their accumulation in the surface layers of the product directly contacting with heated parts of forming machines. The research of the top layer of a poly(vinyl chloride) profile has shown that the surface layer of polymer contains a number of chlorinated hydrocarbons. The following substances have been identified during the research of the hydrocarbons composition contained of the surface layer: hexachlorobenzene, hexachlorobutene, chloroform, acetyl chloride, bi-phenyl, anthracene, naphthalene, and other hydrocarbons. The difference of calculated activation energy of thermooxidizing destruction of surface and internal layers of a polymeric product reveals the process of partial destruction of a surface layer. Data about semivolatile substances, concentrating in polymer surface during processing will be used for development of stabilizers, ecology, and polymer-manufacturing techniques. (c) 2008 Wiley Periodicals, Inc.