Temperature Effects on the Body

The objective of cold protection is to prevent the internal core body temperature from falling below 96.8°F. Maximum severe shivering occurs when the core body temperature is 95°F. Lower body temperatures will likely result in reduced mental alertness, reduction in rational decision making, or loss of consciousness with the threat of fatal consequences. Pain to the extremities may be the first and earliest warning of cold stress.

The following core temperatures are important to know:

• 88.8° to 89.6° – Consciousness clouded, blood pressure becomes difficult to obtain, pupils dilated but react to light, shivering ceases

• 84.2° to 86° – Progressive loss of consciousness; muscular rigidity increased; pulse and blood pressure difficult to obtain; respiratory rate decreases

• 69.8° to 71.6° – Maximum risk of ventricular fibrillation

Clothing and Related Personal Protective Equipment (PPE)

Adequate insulating dry clothing to maintain core temperatures above 96.8° must be provided to workers if work is performed below 40°. Workers with circulatory problems require special precautionary protection against cold injury. Provisions for additional body protection are required if work is performed in an environment at or below 39.2°. For exposed skin, continuous exposure should not be permitted when the air speed and temperature results in an equivalent chill temperature of -25.6°.

If fine work is to be performed with bare hands for more than 10 to 20 minutes below 60.8°, special provisions should be established for keeping the workers’ hands warm. If the air temperature is 0° or less, the hands should be protected by mittens. Please note that superficial or deep local tissue freezing will occur only at temperatures below 30.2°, regardless of wind speed. Workers handling evaporative liquid below 39.2°, such as gasoline, alcohol and cleaning fluids should take special precautions to avoid soaking of clothing or gloves with liquids because of the added danger of cold injury due to evaporative cooling. When cold surfaces below 19.4° are within reach, a warning should be given to each worker to prevent inadvertent contact by bare skin. Eye protection for workers employed outdoors in a snow or ice covered terrain should be supplied. Eye protection should protect against ultraviolet light and glare as well as blowing ice crystals.

Shelter and Hydration

If work is performed continuously in the cold at an equivalent chill temperature at or below 19.4°, heated warming shelters should be made available nearby. Warm sweet drinks and soups should be provided and coffee should be limited. High caffeine type beverages generally should be limited due to the diuretic effects of the liquids, which can result in dehydration.

Extreme Cold Conditions

For work at or below 10.4° workers should be under constant supervision and work rates should not be so high as to cause sweating and soaking of the interior liner of clothes. Rest periods should be provided if heavy work is unavoidable. New employees should not be required to work fulltime in the cold during the first days of employment and the work should be arranged in such a way that sitting still or standing still for long periods is minimized. Workers should be trained in:

• Proper rewarming procedures and appropriate first aid

• Proper clothing practices

• Proper eating and drinking habits

• Recognition of impending frostbite

• Recognition of signs and symptoms of impending hypothermia or excessive cooling of the body even when shivering does not occur

• Safe work practices

Exclusions and Special Medical Provisions

Employees should be excluded from work at 30.2° if they are suffering from disease or taking medication which interferes with normal body temperature regulation or reduces tolerance to cold. Trauma sustained in freezing or subzero conditions requires special attention because an injured worker is predisposed to cold injury. Special provisions should be made to prevent the injured individual from falling into a hypothermic state and also prevent any freezing of exposed tissue.

References

American Conference of Government Industrial Hygienists (2012). Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices. Signature Publications.