The article outlines new edition of a project "Sanitary norms of microclimate in industrial compartments". Up-to-date scientific data, results of studies concerning human heat state in experimental and industrial conditions, evaluation of the workers' health state helped to modify optimal and allowable parameters of microclimate, to rectify requirements for measurement conditions and measuring devices. When the recommended temperature could not be maintained, the duration of work in such conditions should be limited for prevention of overheating and overcooling. To examine prophylactic measures against overheating, the authors suggested an integral characteristic of heating environmental load (TNS-index) and set its safe values.