The series of standards presented in this paper provides a useful package for assessment and design of HVAC systems and protective equipment to be used in moderate, cold, and hot environments. The standards may be used to estimate the optimal combination of environmental thermal factors that will provide comfortable or tolerable healthy working conditions. The standards may also be used to establish optimal work/rest schedules for environments where the working time must be limited owing to strain on the human body. Several of these standards are being adopted as national standards in several countries.

Some of the methods used in the standards are based on many years of re­search and validation, while others are relatively new and not validated to the same degree. It is therefore important to realize that a standard is not an ever­lasting document, but must be revised on a regular basis. These revisions take place at least every fifth year, and experience with use and new knowledge are incorporated into the review process.