Cold Stress

What is cold stress?

Cold stress occurs by driving down the skin temperature, and eventually the internal body temperature. When the body is unable to warm itself, serious cold-related illnesses and injuries may occur, and permanent tissue damage and death may result.

Four factors contribute to cold stress: cold temperatures, high or cold wind, dampness and cold water.  A cold environment forces the body to work harder to maintain its core temperature.  Cold air, water, and snow all draw heat from the body. So, while it is obvious that below freezing conditions combined with inadequate clothing could bring about cold stress, it is important to understand that it can also be brought about by temperatures in the 50's coupled with rain and/or wind.

Types of Cold Stress and Their Symptoms and Treatment

Immersion/Trench Foot

Trench foot is a non-freezing injury of the feet caused by prolonged exposure to wet and cold conditions.

What are the symptoms of trench foot?

Reddening skin, tingling, pain, swelling, leg cramps, numbness, and blisters.

First Aid

  • Remove wet shoes/boots and wet socks.
  • Dry the feet and avoid working on them.
  • Keep affected feet elevated and avoid walking. Get medical attention.

Frostbite

Frostbite is caused by the freezing of the skin and tissues. Frostbite can cause permanent damage to the body, and in severe cases can lead to amputation. Frostbite typically affects the extremities, particularly the face, ears, fingers and toes.

What are the symptoms of frostbite?

Reddened skin develops gray/white patches in the fingers, toes, nose, or ear lobes; tingling, aching, a loss of feeling, firm/hard, and blisters may occur in the affected areas.

First Aid

  • Protect the frostbitten area, e.g., by wrapping loosely in a dry cloth and protect the area from contact until medical help arrives.
  • DO NOT rub the affected area, because rubbing causes damage to the skin and tissue.
  • Do not apply snow or water. Do not break blisters.
  • DO NOT try to re-warm the frostbitten area before getting medical help.

Hypothermia

Hypothermia occurs when the normal body temperature (98.6°F) drops to less than 95°F. Hypothermia is most likely at very cold temperatures, but it can occur even at cool temperatures (above 40°F) if a person becomes chilled from rain, sweat, or immersion in cold water.

What are the symptoms of hypothermia?  

  • Mild Hypothermia: Alert but Shivering
  • Moderate to Severe Hypothermia: shivering stops; confusion; slurred speech; heart rate/breathing slow; loss of consciousness; death.

First Aid

  • Call 911 immediately in an emergency. 
  • To prevent further heat loss: 
    • ​​​​​​​​​​​​​​Move the worker to a warm place.
    • Change to dry clothes.
    • Cover the body (including the head and neck) with blankets, and with something to block the cold (e.g., tarp, garbage bag). Do not cover the face.
  •  If medical help is more than 30 minutes away: 
    • Give warm, sweetened drinks if alert (no alcohol). 
    • Apply heat packs to the armpits, sides of chest, neck, and groin

Preventing Cold Stress

Planning for work in cold weather is the most important defense in preventing cold stress.  Wearing appropriate clothing and being aware of how your body is reacting to the cold are important to preventing cold stress.  Avoiding alcohol, certain medications and smoking can also help to minimize the risk.

Protective Clothing

Wearing the right clothing is the most important way to avoid cold stress.  The type of fabric also makes a difference.  Cotton loses its insulation value when it becomes wet.  Wool, on the other hand, retains its insulative qualities even when wet.

Work Practices

  • Drinking:  Drink plenty of liquids, avoiding caffeine and alcohol.  It is easy to become dehydrated in cold weather.
  • Work Schedule: If possible, heavy work should be scheduled during the warmer parts of the day.  Take breaks out of the cold. Two examples of work schedules are at the bottom of the page.
  • Buddy System: Try to work in pairs to keep an eye on each other and watch for signs of cold stress.  Victims of hypothermia may not recognize symptoms.

Work Schedules

The American Conference of Governmental Industrial Hygienists (ACGIH) developed the following Work/Warm-up Schedules for a 4-hour shift takes both air temperature and wind speed into account, to provide recommendations on scheduling work breaks and ceasing non-emergency work. The first schedule is for light work (mostly standing, little to no movement) and the second is for moderate to heavy work.

ACGIH Work/Warm Schedule for Light Work Over a 4-Hour Shift

  No Wind 5 mph Wind 10 mph Wind 15 mph Wind 20 mph Wind
Air Temperature in °F
Sunny Sky
Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks
10 to 14 No recommendations No recommendations No recommendation No recommendation 120 min
5 to 9  120 min.  1 120 min  1
0 to 4 120 min 1 120 min  1 75 min 2
-1 to -5 120 min  1 120 min  1 75 min 2 55 min 3
-10 to -14 120 min 1 120 min 1 75 min 2 55 min 3 40 min 4
-15 to -19  120 min 1 75 min 2 55 min 3 40 min 4 30 min 5
-20 to -24 75 min 2 55 min 3 40 min 4 30 min 5 Non-emergency work should stop. 
-25 to -29 55 min 3 40 min 4 30 min 5 Non-emergency work should stop. 
-30 to -34 40 min 4 30 min 5 Non-emergency work should stop. 
-35 to -39 30 min 5 Non-emergency work should stop. 
-40 to -44 Non-emergency work should stop. 
-45 to below

 

ACGIH Work/Warm Schedule for Moderate and Heavy Work Over a 4-Hour Shift

  No Wind 5 mph Wind 10 mph Wind 15 mph Wind 20 mph Wind
Air Temperature in °F
Sunny Sky
Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks Max Work Period No. of 10 min. Breaks
5 to 9  No recommendations No recommendations No recommendation No recommendation 120 min 1
0 to 4 120 min 1 120 min  1
-1 to -5 120 min 1 120 min  1 75 min 2
-10 to -14 120 min  1 120 min  1 75 min 2 55 min 3
-15 to -19 120 min 1 120 min 1 75 min 2 55 min 3 40 min 4
-20 to -24  120 min 1 75 min 2 55 min 3 40 min 4 30 min 5
-25 to -29 75 min 2 55 min 3 40 min 4 30 min 5 Non-emergency work should stop. 
-30 to -34 55 min 3 40 min 4 30 min 5 Non-emergency work should stop. 
-35 to -39 40 min 4 30 min 5 Non-emergency work should stop. 
-40 to -44 30 min 5 Non-emergency work should stop. 
-45 to below Non-emergency work should stop. 

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