This International Standard describes methods for measuring and interpreting the following physiological parameters: — body core temperature; — skin temperatures; — heart rate; — body-mass loss. The choice of variables to be measured and techniques to be used is at the discretion of those responsible for the health of the employees. These persons will have to take into account not only the nature of the thermal conditions, but also the degree of acceptance of these techniques by the employees concerned. It should be emphasised that direct measurements on the individual can only be carried out on two conditions. a) If the person has been fully informed about the discomfort and the potential risks associated with the measurement technique and gives free consent to such measurements. b) If the measurements present no risk for the person which is unacceptable in view of general or specific codes of ethics. In order to simplify this choice, Annex A presents a comparison of the different methods concerning their field of application, their technical complexity, the discomfort and the risks that they might involve. This standard defines the conditions which are to be met in order to ensure the accuracy of the data gathered from the different methods. The measurement methods are described in Annex B. Limit values are proposed in Annex C (informative). This standard is not concerned with experimental conditions for which investigators may develop alternative methods intended to improve knowledge in this area. It is however recommended, when conducting such studies in the laboratory, to use the methods described below as references, so that results may be compared. Before using the evaluations methods described in this International Standard, the user is required to follow the ethics and legal rules in force in his country or institution. Accordingly, ethical committees will be consulted and rules concerning free written consent, freedom of participation, confidentiality, etc. will be strictly followed.