Keeping the Chill Out: Working Safe in Cold Weather

Dec. 1, 2010
When working in cold temperatures, the best defense is common sense. Knowing what to wear, what to eat and drink and what to do if an employee is suffering from a cold-related illness can save lives.

As the winter months approach, we must pay attention to anyone who might be working or playing in cold environments.

Working in a cold environment can involve several adverse effects on human performance and health. Workers suffering from exposure to the cold can experience thermal discomfort, increased strain, decreased performance and cold-related diseases and injuries. Cold also can modify or aggravate the risk of common hazards and increase the risk of cold-associated injuries.

A number of industries and occupations involve substantial outdoor cold exposure. These include construction workers, postal workers, delivery people, utility and telecommunication workers, firefighters, police and others. Many indoor workers — such as those in the food processing industry, cold storage industry, supermarkets or in the transportation chain — also can be negatively impacted by cold work environments if not properly protected and trained.


Cold temperatures have hazardous effects on humans and their ability to work well. When the body is exposed to cold temperatures, the negative effects can include dehydration, numbness, shivering, frostbite, immersion foot and hypothermia.

These negative effects are experienced first by the peripheral parts of the body and gradually progress to deep body tissues and the body core. When the body's core temperature drops below 95 F/35 C, it is defined as hypothermia, which along with frostbite is one of the more extreme dangers of prolonged work in cold environments.

Frostbite is a severe reaction by the skin to cold that can permanently damage fingers, toes, the nose and the ear lobes. Frostbite actually freezes and crystallizes the fluids in the body tissues and cellular spaces. This can damage the blood vessels, causing blood clotting and lack of oxygen to the affected area and deeper tissues. In severe cases, frostbite can kill and damage tissue to the extent that an amputation may be required.

Factors that influence how severe frostbite can be include the length of time an employee is exposed to the cold, the temperature outside, the wind chill factor (force of the wind), the amount of humidity in the air, dampness of clothing, high altitudes and whether the person has ingested alcohol or other drugs.

Alcohol and drugs can impair thinking, which can cause more damage due to lack of common sense in caring for the affected area. It also can cause further constriction of blood vessels, which prevents warm blood from reaching affected areas, worsening the frostbite. Frostbite can occur in just a few minutes if conditions are cold enough with a high wind-chill factor on unprotected body parts, for example, the ears.

Some employees are at higher risk of frostbite. Those at risk include older employees, those with circulation problems, anyone with a previous history of frostbite, those who ingest alcohol, use nicotine or take beta-blocker medications. Employees who have had a recent injury or blood loss also are at a higher risk of frostbite. Employees who do not take precautionary measures, such as wearing the appropriate protective clothing to prevent frostbite, also are at high risk. Training for all employees in the dangers of cold temperatures is essential.


Mild frostbite (frostnip) affects the outer skin layer and appears as a blanching or whitening of the skin. These symptoms usually disappear as the affected area warms. The skin may appear red for several hours.

Superficial frostbite can result in blistering. The skin feels numb, waxy and frozen, and can look grayish-yellow, grayish-blue or white. Ice crystals form in the skin cells and the rest of the skin remains flexible.

Deep frostbite is the most serious of frostbite cases. Sensation usually is absent in the affected area and blistering usually does not occur. The blood vessels, muscles, tendons, nerves and bone may be frozen. This can lead to permanent damage, blood clots and gangrene, which ultimately can lead to amputation and even death if professional medical attention is not obtained as soon as possible.

Other symptoms that indicate frostbite include swelling, itching, burning and deep pain as the area is warmed.

It is normal to feel pain in the affected area as it is rewarmed. Treatment of frostbite is best performed by trained medical professionals. But if you cannot get to help right away, you can do some simple things to assist someone to warm up.

It is best to get to a warm place where the employee can stay dry and warm after re-warming the body part(s). Use warm (100 F/38 C), not hot, water for 30-45 minutes until a good “flush” or reddening of color has returned to the skin. Do not place affected extremities near a fire. It can cause burns due to the lack of sensation in the affected area. You can place affected areas under the armpits or groin area for re-warming as well.

Once an area is re-warmed, it is imperative to keep the area from re-freezing. If re-freezing occurs, this is very serious and can cause permanent damage. It is better to delay warming if there is a chance the area can refreeze while trying to make it to permanent shelter.

Do not thaw the injury with melted snow or ice. Do not rub the area with snow. Finally, avoid alcohol, nicotine and other drugs that can further restrict the blood flow to the affected area.

In summary, frostbite is a serious condition that can be prevented if you plan ahead, properly train the employees in recognizing signs and symptoms and the employees know the appropriate clothing and fabric to wear.


Hypothermia is a dangerously low body temperature. It occurs when more heat is lost than the body can generate. It usually is caused by extended exposure to the cold. Hypothermia can kill amazingly fast when cold temperatures and strong winds cause the body to quickly lose heat. Symptoms of hypothermia start with shivering, which is the body's attempt to heat from rapid muscular shaking. When the body's temperature drops to below 95 F/35 C, shivering stops and dizziness and disorientation begin.

At this point, the body only maintains heat around its vital organs — brain, heart and lungs — and shuts down circulation to the arms and legs. The heart rate becomes slow, intermittent and weak, and the blood vessels widen. This makes a person feel hot and want to remove all of his clothes before he finally slips into unconsciousness. Ultimately, the heart stops.

The risk of hypothermia is significantly higher when temperatures are below freezing, although anything that is below body temperature (98.6 F/37 C) can explain hypothermia, especially in older employees.

Employees who are wearing inappropriate clothing are at higher risk for hyphothermia, as are employees who are wet, tired, dehydrated or suffering from malnutrition. The risk of hypothermia is greater if alcohol is consumed, because alcohol makes blood vessels dilate, providing a larger surface area through which heat can be lost.

As with frostbite, it is easier to prevent hypothermia than it is to treat it. It is important to have everyone working outdoors trained in the recognition of symptoms. If a supervisor or coworker suspects a person might have symptoms of hypothermia, a rapid response could save a life.

Symptoms of mild hypothermia include a core temperature between normal and 96 F/35.5 C, involuntary shivering and the inability to do things requiring motor skills. Moderate hypothermia means a core temperature between 95 F/35 C and 93 F/33 C. Symptoms include confused thought processing, loss of general motor control, slurred speech, aggressive shivering and, finally, the perception that the person feels hot.

Severe hypothermia rapidly can cause death. The core temperature is between 92 F/33 C and 86 F/30 C. The person has a pale, whitish skin tone and dilated pupils. Waves of aggressive shivering are followed by pauses, which get longer until the shivering finally stops. At this point, the body recognizes that it is not creating enough heat and chooses to retain the energy instead.

The body goes into hibernation and the worker will appear dead, although he actually might still be alive. In cases of fatal hypothermia, the core temperature falls below 86 F/30 C, breathing becomes erratic, the person becomes unconscious and the heart stops.


There are ways to assess the stages of hypothermia:

  • Ask the employee to stop shivering. If he can, then hypothermia most likely is mild.
  • Ask the employee a mathematical question. If he can do it, then hypothermia is most likely mild.
  • If you can't find a pulse at the person's wrist, then this can be a sign of a core temperature of less than 90 F/32 C, indicating severe hypothermia.
  • If the employee is in a fetal position, try to open his arms. If they curl back then the person still is alive, because dead muscles will not contract.

In the event of mild hypothermia, add dry clothing layers, increase movement, move the employee out of the cold, use another person's body heat to help warm the employee and encourage the employee to stay well hydrated and maintain proper levels of nutrition. The employee can drink something warm (not caffeine, which is a diuretic, or alcohol, which increases heat loss) and eat something sugary, something with carbohydrates and something with fats to gain immediate, slow release and stored energy,

In the event of hypothermia, the first option is to seek professional medical help. Knowing medical response may take some minutes to arrive, it is imperative to begin practical re-warming techniques, especially in the case of moderate or severe hypothermia. The idea behind re-warming is to preserve any heat the employee might have and replenish what has been lost. Here are a few techniques:

Start inhalation re-warming. This warms up the body's critical core, along with the head and neck. More importantly it warms the hypothalamus, which is situated at the bottom of the brainstem and plays a vital part in the central nervous system. Inhalation re-warming involves the individual breathing in warm (about 122 F/45 C), moist air.

This can be done with professional equipment, or by breathing directly above, but not covering the individual's mouth and nostrils. It sends vital heat directly to the areas it is needed most, and so can be very effective, especially in raising an individual's level of consciousness. It also is a good method as it reduces respiratory heat loss, which can account for up to 30 percent of the body's total heat loss. This particularly is important if the surrounding air is below freezing.

Keep the employee's movements to a minimum. Making the muscles work at this stage likely will send cold blood from the legs and arms into the central circulatory system. This will cause the core temperature to fall even more, which could be fatal; when the heart is cold, its natural rhythm is disturbed.

Provide a hypothermia wrap. This works on the principle that a person can regenerate their heat better than any external heat source. Have these wraps, which look like metallic blankets, available on trucks, industrial equipment or in the first aid box. Shivering alone can produce 2C per hour. The individual must be dry and in a dry place because any exposure to moisture will result in further heat loss. Place a warm covering and clothing and at least one aluminum blanket directly on top of each other on the floor and position the person on top, face up. Fold the employee in a secure wrap.

Provide warm sugar water. Give the employee a diluted mix of sugar and warm water every 15 minutes. This allows direct absorption when the body cannot digest real food. It provides the energy needed so the person can re-warm.

Encourage urination. A full bladder conducts heat away from the body and so urinating frequently solves this. The person may need to be assisted.

Apply heat to the major arteries in the neck, armpit, groin and palms, using hot water bottles or warm towels.


As with any workplace hazard, prevention is key to protecting employees. Here are tips to prevent cold-related illness:

  • Eat properly with plenty of carbohydrates and fats for energy and warmth prior to beginning work.

  • Drink fluids. If a person doesn't get up in the night at least once to urinate then they are not drinking enough. Urine should be a pale yellow, straw-like color, not dark.

  • Get enough sleep. Outdoor work is hard and cannot be done on only a few hours of sleep. Being well rested will make employees feel energized and positive.

  • Remove any wet clothes immediately. They cause accelerated heat loss and impair movement.

  • Insulate well, particularly the head and neck as these are the areas that lose the most heat the quickest.

  • Wear proper winter clothing that insulates from the cold and lets perspiration evaporate while protecting from the wind, rain and snow. Protect feet and toes. Wear two layers of socks — cotton underneath a pair of wool socks is best — with a pair of well-fitted boots that come above the ankle.

  • Hand protection is vital. Mittens are warmer than gloves, but can limit dexterity. Wear a pair of gloves under a pair of mittens for warmth, and remove mittens to use gloved fingers as needed.

Because of the negative impact of cold on human health and performance, as well as on work productivity, quality and safety, the ISO standard-setting organization felt a comprehensive strategy of risk assessment and management practices and methods was needed for work in cold environments. Headquartered in Geneva, ISO is a network of the national standards institutes of 157 countries and is the world's largest developer and publisher of international standards.

The ISO standard 15743:2008, “Ergonomics of the Thermal Environment — Cold Workplaces — Risk Assessment and Management,” gives practical instructions for risk analysis and management in cold working conditions. It describes:

  • A model and methods for risk assessment practices in cold work.

  • A model and method for occupational health care professionals to identify individuals having symptoms that increase their cold sensitivity, plus optimal guidance and instructions for individual cold protection.

  • Informative guidelines on how to apply different international thermal standards and other validated scientific methods when assessing cold-related risks.

  • A model and methods for cold risk management practices.

  • Practical examples of working in cold conditions.

“ISO 15743:2008 complements a series of ISO standards concerned with work in cold conditions as well as other areas of thermal stress,” said Professor Ken Parsons, chairman of the ISO subcommittee that developed the standard. “It supports good occupational health and safety practice and will help developers, manufacturers, management, occupational safety personnel, occupational health care workers and others.”

Cynthia Roth is founder and CEO of Ergonomic Technologies Corp. and is a member of EHS Today's editorial advisory board.

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