This International Standard specifies a procedure for determination of the mass concentration of mercury vapour in workplace air using a method of gold-amalgam collection with analysis by either cold vapour atomic absorption spectrometry (CVAAS) or cold vapour atomic fluorescence spectrometry (CVAFS). The procedure specifies a number of sampling methods for different applications. When it is known that no particulate inorganic mercury compounds are used in the workplace and that none are produced in the processes carried out, samples of mercury vapour are collected using a pumped sorbent tube containing porous gold-coated diatomaceous earth. Suitable sorbent tubes are commercially available or they can be made from sorbent prepared by pyro-decomposition of chloroauric acid [hydrogen tetrachloroaurate(III)] sintered on diatomaceous earth. When both mercury vapour and particulate inorganic mercury compounds could be present in the test atmosphere, samples of mercury vapour are collected using a pumped sorbent tube fitted with a quartz fibre prefilter to remove particulate inorganic mercury compounds. If desired, the procedure described in ISO17733 can be used to collect and analyse separate samples for measurement of particulate inorganic mercury compounds. When it is known that no elemental mercury is used in the workplace and that no mercury vapour is produced in the processes carried out, the procedure described in ISO17733 can be used, if desired, to collect and analyse samples for measurement of particulate inorganic mercury compounds. The procedure is highly sensitive and suitable for static sampling or for determination of short-term personal exposure to mercury vapour in workplace air. The lower limit of the working range of the procedure is governed by the lower limit of the analytical range of the CVAAS or CVAFS instrument, which is approximately 0,01ng of mercury for a sorbent tube containing 80mg of sorbent (see 13.1). The upper limit of the working range of the procedure is governed by the upper limit of the analytical range of the CVAAS or CVAFS instrument, e.g. about 1μg of mercury (see 13.2). The sampling capacity of one commercially available sorbent tube has been shown to be greater than 2μg. The concentration ranges of mercury in air for which the procedure is applicable are determined in part by the sampling method selected by the user. The procedure is suitable for making short-term measurements (e.g. 15min) when sampling at a flow rate of between 100ml min−1 and 1000ml min−1 using a commercially available sorbent tube. For assessment of long-term exposure, such as 8h, this procedure can be used with sampling flow rate of 100ml min−1 in workplaces where the concentration of mercury vapour is expected to be lower than 20μg m−3. If the expected concentration of mercury vapour is higher than 20μg m−3, it is necessary to use the procedure prescribed in ISO17733. The method is unsuitable for making measurements of mercury vapour in air when chlorine is present in the atmosphere, e.g. in chloralkali works (see 13.8.1). Gaseous organo-mercury compounds can cause a positive interference (see 13.8.2).