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37--Industrial Hygiene <0 TABLE 37-G THRESHOLD LIMIT VALUES FOR PHYSICAL AGENTS, 1973 {Continued) III. Work-rest regimen The permissible exposure limits specified in Table I and Diagram A are based on the assumption that the WBCT value of the resting place is the same or very close to that of the work place If the resting place is air conditioned and its climate is kept at or below 24 C (75 F), WBCT, the allowable resting time may be reduced by 25% The permissible exposure limits for continuous work are applicable where there is a work-rest regimen of a 5-day work week and an 8-hour work day with a short morning and afternoon break (ap proximately 15 minutes) and a longer lunch break (approximately 30 minutes) Higher exposure limits are permitted if ad ditional resting time is allowed All breaks, including unscheduled pauses and administrative or operational waiting pe riods during work may be counted as rest time when additional rest allowance must be given because of high environmental temperatures It is a common experience that when the work on a job is self-paced, the workers will spontaneously limit their hourly work load to 30-50 percent of their maximum physical performance capacity They do this either by setting an appropriate work speed or by interspersing unscheduled breaks Thus the daily average of the workers' metabolic rate seldom exceeds 330 kcal/hr However, within an 8-hour work shift there may be periods where the workers' hourly average metabolic rate will be higher IV. Water and salt supplementation During the hot season or when the worker is exposed to artificially generated heat, drinking water shall be made avail able to the workers in such a way that they are stimulated to frequently dnnk small amounts, i e, one cup every 15-20 minutes (about 150 ml or % pint) The water shall be kept reasonably cool (10-15 C or 50 0-60 0 F) and shall be placed close to the workplace so that the worker can reach it without abandoning the work area The workers should be encouraged to salt their food abundantly dunng the hot season and particularly during hot spells If the workers are unacchmatized, salted drinking water shall be made available in a concentration of 0 1 percent (lg NaCl to 1 0 liter or 1 level tablespoon of salt to 15 quarts of water) The added salt shall be completely dissolved before the water is distributed, and the water shall be kept reasonably cool V. Other Considerations A Clothing The permissible heat ex posure TLVs are valid for light summer clothing as customarily worn by workers when working under hot environmental conditions If special clothing is required for performing a particular job and this clothing is heavier or it impedes sweat evaporation or has higher insulation value, the worker'$ heat tolerance is reduced, and the permissible heat exposure limits in dicated in Table 1 and Figure 1 are not applicable For each job category where special clothing is required, the permissi ble heat exposure limit shall be established BTU'rw Role of Work Fro 1--Permissible Heat Exposure Thresh old Limit Value by an expert B Acclimatization and Fitness- The rec ommended heat stress TLVs are valid for acclimated workers who are physically fit Ionizing Radiation See U S Department of Commerce Na tional Bureau of Standards, Handbook 59, "Permissible Dose from External Sources of Ionizing Radiation," September 24, 1954, and addendum of April 15, 1958 A report, Basic Radiation Protection Cri teria, published by the National Commit tee on Radiation Protection, revises and