This International Standard gives general guidance for the sampling and analysis of airborne toluene diisocyanate (TDI) in workplace atmospheres. The procedure specified in this International Standard is especially suitable for short (15 min) and long-term (4 h) sampling and analysis of 2,4- and 2,6-TDI vapours.The upper limit for this method is approximately 85 µg of TDI per sample. This is a conservative upper limit based on the requirement of maintaining a sufficient amount of reagent on the coated glass fibre filter while permitting a 4 h sample to be collected at 1 l/min from an atmosphere containing 50 nl/l of TDI.The quantitation limits for this method are 0,039 µg for 2,4-TDI and 0,034 µg for 2,6-TDI using a fluorescence detector. These limits, for a 15-min sample collected at 1 l/min, are equivalent to 0,36 nl/l for 2,4-TDI, and 0,32 nl/l for 2,6-TDI. For a 4 h sample collected at 1 l/min, the limits are equivalent to 0,022 nl/l for 2,4-TDI and 0,020 nl/l for 2,6-TDI.The commercial availability of the specified reagents, the use of common analytical instrumentation, and the current widespread use of the method make this standard method ideally suited for the determination of TDI in workplace environments.