To understand the risk of exposure to a substance or a mixture of substances the risk assessor requires information on the hazards of the substance(s). The hazard information can be found in the Safety Data sheet and from hazard classification such as GHS hazard statements. In addition to understand the risk of exposure to an individual or worker group the level of exposure needs to be understood. The “best” method of doing this is by conducting a measurement campaign using suitable occupational hygiene sampling and analysis techniques, both conducted by a competent person. In many instances this is not possible and in the place of occupational hygiene monitoring modelling tools can be used which take parameters related to the substance(s), the workplace and the task/activity being conducted. Examples of such modelling tools are provided in the links below. Such tools can be further defined as lower tier tools such as ECETOC TRA and COSHH essentials, where the output is more conservative and the higher tier tools such as Stoffenmanager and ART where more parameters are required to give a more accurate prediction of exposure. All of the tools require some level of competence and training in use. Advice and help are provided on the websites for each tool.