Abstract Isocyanates are found in a vast number of products (paints, insulating foam, glues, etc.) and are therefore widely used in many industries (automotive, construction, furniture manufacture, etc.). However, they can be harmful to respiratory and dermal health; in fact, isocyanate exposure is the leading cause of occupational asthma in Québec. The aim of the Industrial Hygiene Guide for Safe Use of Isocyanates is to inform and support occupational health and safety actors (safety practitioners, hygienists, etc.) as well as employers and workers in their efforts to prevent the risks associated with isocyanate exposure. This Guide is based on an industrial hygiene approach. It explains the chemical risks linked to isocyanates so that informed decisions can be made about the preventive measures to be implemented. It constitutes a unique source of information on environmental evaluation. In addition, it gives examples of work situations according to the process used (for example, spray application of a coating), which will make it easier to understand and manage exposure to this toxic substance. This second edition is, without a doubt, the most complete and up-to-date work aimed at preventing the risks inherent in isocyanate use.