This analytical method is a validated measurement procedure for the determination of ethylene oxide [75-21-8] in workplace air averaged over the sampling period after personal or stationary sampling. Sampling is performed by drawing air through a tube filled with activated charcoal. The flow is set to 25 ml/min with a recommended air sample volume of 6 l. Sampling is performed over 40 min. The adsorbed ethylene oxide is desorbed using a toluene/carbon disulphide mixture (90+10 v/v) and converted to 2-bromoethanol using hydrobromic acid after the phases have separated and been filtered. The sample is analysed by means of gas chromatography (GC) with a mass selective detector (MSD). The quantitative evaluation is based on a calibration function obtained by means of a multiple-point calibration. The relative limit of quantification (LOQ) is 7 μg/m³ ethylene oxide for an air sample volume of 6 l. The mean recovery was 94% and the expanded uncertainties were between 20 and 21%.