Course 602 - Heat and Cold Stress Safety

Safety guides and audits to make your job as a safety professional easier

Cold Stress and Safety



Anyone working in a cold environment may be at risk of cold stress. Some workers may be required to work outdoors in cold environments and for extended periods, for example, snow cleanup crews, sanitation workers, police officers and emergency response and recovery personnel, like firefighters, and emergency medical technicians.

When the body is unable to warm itself, cold related stress may occur. Cold stress occurs by driving down the skin temperature and eventually the internal body temperature (core temperature). Over time, your body will begin to shift blood flow from your extremities (hands, feet, arms and legs) and outer skin to the core areas (chest and abdomen). This allows exposed skin and the extremities to cool rapidly and increases the risk of frostbite and hypothermia. Combine this with cold water, and trench foot may also be a problem. This may lead to serious health problems, and may cause tissue damage, and possibly death.

Risk factors that contribute to cold stress include:

  • Cold air temperatures,
  • high velocity air movement,
  • wetness/dampness of the air,
  • dressing improperly,
  • exhaustion or poor physical conditioning, and
  • predisposing health conditions (e.g., hypertension, hypothyroidism, and diabetes)

1. Why does exposed skin and the extremities cool rapidly in cold temperatures?

a. Heat does not transfer as rapidly to organs
b. Blood becomes thicker causing low heat transfer
c. Blood flow shifts to supply core areas
d. Blood flow slows at lower temperatures

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Wind Chill

Wind Chill Chart
Wind Chill Chart - U.S. Army. Click to enlarge.

Wind chill is the temperature your body feels when air temperature and wind speed are combined. The wind chill temperature is how cold people and animals feel when outside. Wind chill is based on the rate of heat loss from exposed skin caused by wind and temperature, however, research has shown that relative humidity is not a significant factor affecting wind chill.

As the wind increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature. Therefore, the wind makes it FEEL much colder. For instance, if the temperature is 0°F and the wind is blowing at 15 mph, the wind chill is -19°F. At this wind chill temperature, exposed skin can freeze in 30 minutes. See the Wind Chill Chart to learn more.

While it is obvious that below freezing conditions combined with inadequate clothing could bring about cold stress, it is also important to understand it can also be brought on by warmer temperatures (such as 50°F) combined with some rain and wind.

2. Which of the following are the two primary factors affecting wind chill?

a. Exposure and humidity
b. Humidity and temperature
c. Wind and humidity
d. Wind and temperature

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Common Cold-Induced Problems


If you are not careful while working in cold temperatures, hypothermia could be the result.

Hypothermia means "low-heat," which is a potentially serious health condition. This occurs when body heat is lost faster than it can be replaced. When the core body temperature drops below the normal 98.6°F to around 95°F, you will see the following symptoms:

  • Uncontrollable shivering
  • Slow speech
  • Memory lapses
  • Frequent stumbling
  • Drowsiness
  • Exhaustion


Without early recognition and active care, hypothermia can be deadly. Here are some things you can do, if you recognize someone who is dealing with hypothermia:

  • Gently move the victim to a warmer place
  • Remove wet clothing
  • Cover the victim with something dry and warm
  • If available, contact Emergency Medical Services. If you are far from professional medical care, start re-warming the person. Place him near a heat source and put containers of warm water in contact with the skin.
Hypothermia Real Life Scenario

Clink the link to read a

An employee and co-worker were securing a large tug boat that broke loose during a storm and was drifting towards waterfront homes. The two employees off-boarded the work boat and boarded the tug boat.

At some point, the work boat became detached from the tug boat and drifted away. One of the employees dove into the frigid water to catch the work boat. However, he could not reach it and re-boarded the tug boat. He found another smaller vessel on board the tug boat and boarded it. He was going to float out to get the work boat.

The small boat capsized and the employee was hanging onto the boat, waiting for rescue workers. The rescue took about 45 minutes. He was transferred to a hospital and later died from complications related to hypothermia.

3. When do the symptoms of hypothermia begin to appear?

a. When the core temperature lowers to 85°F
b. When the peripheral temperature reaches 90°F
c. When the core temperature drops to about 95°F
d. When the peripheral temperature dips below 98°F

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Common Cold-Induced Problems (Continued)


Frostbite is a reaction to cold exposure - U.S. Army.

Frostbite is a severe reaction to cold exposure that causes freezing in the deep layers of skin and tissues. Frostbite can cause permanent damage and even cause amputation of the affected area. While frostbite usually occurs when temperatures are 30 degrees Fahrenheit or lower, wind chill factors can allow frostbite to occur in above freezing temperatures.

Frostbite usually affects the extremities, particularly the feet and hands. (see picture) However, frostbite can also affect the ears and nose. The affected body part will be cold, tingling, stinging or aching followed by numbness. The skin color turns red, then purple, then white, and is cold to the touch. There may also be blisters in severe cases.


Early recognition and care for a frostbitten victim can reduce or even eliminate future complications. Minor frostbite can be treated by simply re-warming the area using skin-to-skin contact, such as a warm hand. If more serious, get the person to a warmer place.

Here are some more treatment tips:

  • Remove any jewelry from the affected areas.
  • Place clean pads between frostbitten fingers and toes.
  • Wrap the affected part with a clean towel or pad.
  • Do not rub or massage the affected area or disturb blisters on frostbitten skin.
Frostbite Real Life Scenario

Clink the link to read a

A worker was wearing a thermo-insulated jacket, overalls, and gloves and began work in the freezer department of a supermarket chain warehouse. His work consisted of selecting produce off warehouse shelves and delivering the product to the designated freezer truck.

At the completion of the eight-hour work shift, he went home and soon realized that he was in unbearable pain and the toes on both his feet were black and blistering. He immediately left the house and went to the hospital where his feet were treated for frostbite and he was hospitalized.

4. What condition is an employee suffering from if the skin color turns red, then purple, then white, and is cold to the touch?

a. Trench Foot
b. Frostbite
c. Hypothermia
d. Cold rash

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Common Cold-Induced Problems (Continued)

Trench foot is caused by having feet immersed in cold water at temperatures above freezing.

Trench Foot

Trench foot, or immersion foot, is caused by having feet immersed in cold water at temperatures above freezing for long periods of time. It is similar to frostbite, but considered less severe. Symptoms usually consist of tingling, itching or burning sensation. Blisters may also be present.


When possible, air-dry and elevate your feet, and exchange wet shoes and socks for dry ones to help prevent the development of trench foot. Treatment for trench foot is similar to the treatment for frostbite. Take the following steps:

  • Thoroughly clean and dry your feet.
  • Put on clean, dry socks daily.
  • Treat the affected part by applying warm packs or soaking in warm water (102° to 110° F) for approximately 5 minutes.
  • When sleeping or resting, do not wear socks.
  • Obtain medical assistance as soon as possible.

If you have a foot wound, your foot may be more prone to infection. Check your feet at least once a day for infections or worsening of symptoms.

5. If the foot is immersed in cold water for long periods of time, what injury to the foot may occur?

a. Frostbite
b. Trench Foot
c. Neuropathy of the foot
d. General hypothermia

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Prevention of Cold Stress

Engineering Controls

Insulating heavy equipment cabs is an effective engineering control method.

Engineering controls can be effective in reducing the risk of cold stress through the design of equipment, materials, and facilities. For example:

  • Radiant heaters may be used to warm workers.
  • Shielding work areas from drafts or wind will reduce the wind chill.
  • Using insulating materials on equipment handles, especially metal handles, when temperatures drop below 30 degrees Fahrenheit.

Work Practice Controls

There are several work practice measures to protect workers in cold environments. Here are a few:

  • Recognize the environmental and workplace conditions that may be dangerous.
  • Learn the signs and symptoms of cold-induced illnesses and injuries and what to do to help workers.
  • Train workers about cold-induced illness and injuries.
  • Encourage workers to wear proper clothing for cold, wet and windy conditions, including layers that can be adjusted to changing conditions.
  • Be sure workers in extreme conditions take a frequent short break in warm, dry shelters to allow their bodies to warm up.
  • Try to schedule work for the warmest part of the day.
  • Use the buddy system-work in pairs so that one worker can recognize danger signs.
  • Avoid exhaustion or fatigue because energy is needed to keep muscles warm.

6. The insulation of equipment and facilities is an example of _____.

a. Elimination or substitution
b. Safe work practices
c. Administrative controls
d. Engineering controls

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Protective Clothing

Protective clothing, such as this warm jacket, is the most important way to avoid cold stress.

Protective clothing is the most important way to avoid cold stress. The type of fabric also makes a big difference. Cotton loses its insulation value when it becomes wet. Wool, silk and most synthetics, on the other hand, retain their insulation even when wet. Workers should wear at least three layers of clothing. There should be an inner layer of wool, silk or synthetic to pull moisture away from the body. The middle layer should include a layer of wool or synthetic to provide insulation, even when wet. Then, an outer wind and rain protection layer is needed to allow some ventilation to prevent overheating.

Here are some other protective clothing recommendations:

  • Wear a hat or hood. Up to 40% of body heat can be lost when the head is left exposed.
  • Wear insulated boots or other footwear.
  • Keep a change of dry clothing available in case work clothes become wet.

Employee Training

Training in recognition and treatment of cold stress is important. Supervisors, workers and co-workers should watch for signs of cold stress and allow workers to interrupt their work if they are extremely uncomfortable. Supervisors should also ensure work schedules allow appropriate rest periods and make sure liquids are available. They should use appropriate engineering controls, personal protective equipment and work practices to reduce the risk of cold stress.

All of these measures should be incorporated into the relevant health and safety plans.

7. Which type of fabric loses its insulative qualities when wet?

a. Synthetics
b. Cotton
c. Wool
d. Silk

Check your Work

Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.



During the winter months, exposure to the cold is an additional occupational hazard. Health problems including frostbite, trench foot and hypothermia can result. This Builders Mutual video discusses how to prevent and respond to each.

Final Exam