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OPERATING PROCEDURES NO. HS-103 COLD STRESS 103.1 PURPOSE The purpose of this section is to establish procedures for the implementation, operation, and monitoring of a cold stress prevention, evaluation, and response program. The cold stress OP also describes the signs and symptoms which characterize excessive exposure of work site personnel to cold environments. Recognition of these signs and symptoms necessitates prompt corrective action to prevent permanent injury or death. 103.2 REQUIREMENTS The American Conference of Governmental Industrial Hygienists (ACGIH) has developed tentative Cold Stress Threshold Limit Values (TLVs) that are intended to protect workers from the severest effects of cold stress (hypothermia) and cold injury. The TLVs are also intended to describe exposures to cold working conditions under which it is believed that nearly all workers can be repeatedly exposed without adverse health effects. The TLV objective is to prevent the deep • body core temperature from falling below 36°C (96.8°F) and to prevent cold injury to body extremities. Deep body temperature is the core temperature of the body as determined by rectal temperature measurements. For a single, occasional exposure to a cold environment a drop in core temperature of no lower than 35°C (950) should be permitted. In addition to provisions for total body protection, the TLV objective is to protect all parts of the body with emphasis on hands, feet, and head from cold injury. 103.3 TYPES OF COLD STRESS Two factors influence the development of a cold injury: ambient temperature and the velocity of the wind. Wind chill (Table HS-103-1) is used to describe the chilling effect of moving air in combination with low temperature. For instance, 10°F with a wind of 15 mph is equivalent in chilling effect to still air at -18 F. As a general rule, the greatest incremental increase in wind chill occurs when a wind of 5 mph increases to 10 mph. Additionally, water conducts heat 240 times faster than air. Thus, the body cools suddenly when chemical-protective equipment is removed if the clothing underneath is soaked with perspiration. Persons working outdoors in temperatures at or below freezing may experience frostbite. Extreme cold for a short time may cause severe injury to the surface of the body. Areas of the body that have a high surface area to volume ratio, such as fingers, toes, and ears, are the most susceptible. 1