1.1 ,This test method describes the determination of 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI) in air samples collected from workplace atmospheres in a cassette containing a glass-fiber filter impregnated with 1-(2-pyridyl)piperazine (1-2 PP). This procedure is effective for determining the vapor content of atmospheres. It is advisable to perform a field extraction for atmospheres containing aerosols to avoid the possibility of an underestimation.