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Working in Cold Environments. Preventing Cold-related Injuries and Illnesses. January, 2011. How the body maintains thermal (heat) balance, constant internal temperature How the body reacts to cold conditions Injuries and illnesses caused by exposure to cold

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Working in Cold Environments

Preventing Cold-related Injuries and Illnesses

January, 2011

what this presentation covers

How the body maintains thermal (heat) balance, constant internal temperature

  • How the body reacts to cold conditions
  • Injuries and illnesses caused by exposure to cold
  • Preventive measures to minimize the hazards from cold exposure
What This Presentation Covers

See the module “Cold-related Injuries and Illnesses” for more detailed descriptions of hypothermia, frostbite, and other cold injuries.


Exposure to cold can occur when working outdoors or in artificial cold environments. Working for prolonged periods or in extreme cold conditions can lead to cold-related injuries and illnesses, permanent tissue damage, and death.

  • Examples of artificial cold environments:
  • Cold storage rooms, refrigerated warehouses
  • Freezers
  • Refrigerated tractor trailers
workers at risk of cold exposure

Examples of industries/jobs at risk of exposure to cold:

Workers at Risk of Cold Exposure
  • Window cleaning
  • Police, fire, and emergency response
  • Postal, delivery services
  • Sanitation/trash collecting
  • Utilities, communications
  • Building, road, and other construction, repair
  • Airport ground personnel/ support
  • Ski resorts and other outdoor recreation
  • Ferries; Longshore/dock work
  • Fishing, crabbing, diving
  • Logging
  • Trucking, other transport
  • Agriculture and dairy
  • Food processing, packing, storage
  • Cold storage, warehousing
  • Ice making
maintaining temperature balancing heat loss and heat production
Maintaining Temperature: Balancing Heat Loss and Heat Production

The body does this through balancing heat loss and heat production.

In cold conditions, the body reduces heat loss and increases heat production.

Most of the body’s energy is used to maintain an internal (core) body temperature of approximately 98.6°F (37°C).

Normal core body temperature:

98.6°F (37°C)

Body’s core area:

(internal organs, especially ones vital for survival)

  • Heart
  • Brain
  • Lungs
  • Liver
  • Kidneys
maintaining temperature balancing heat loss and heat production6
Maintaining Temperature: Balancing Heat Loss and Heat Production

Over time, your body will decrease blood flow to your extremities and outer skin and shift it to the body core to keep the internal organs warm. However, this allows exposed skin and the extremities to cool rapidly and increases the risk of cold-related injuries, such as frostbite and hypothermia.

challenges from cold conditions
Challenges from Cold Conditions

Cold conditions force your body to work harder to maintain its temperature. The challenges you face from a cold environment include:

Air temperature

Wetness: rain, snow, ice, humidity; sweat; wet clothes; water

Air movement: wind speed (5 miles per hour and higher); blown air from fan in cold rooms, etc.

wind chill effect
Wind Chill Effect

Wind chill is the perceived temperature (what it “feels like”) resulting from the effect of wind (wind speed) in combination with cold air (air temperature). The combined effect increases the rate of heat loss from exposed skin. The stronger the wind at a given temperature, the cooler the wind chill will be.

(Refer to Wind Chill Chart on next slide)

Example: When the air temperature is 15°F and wind speed is 10 mph, your exposed skin receives conditions equivalent to the air temperature being 35°F. Frostbite will develop in 30 min.

If the wind speed doubles to 20 mph, it will feel like it’s -42°F and frostbite will occur in only 10 minutes.


Example: If the temperature is -15°F and wind speed is 10 mph, it will feel like it’s -35°F, and frostbite will develop in 30 minutes. If the wind speed doubles to 20 mph, the time for frostbite to occur drops to only 10 minutes.

Wind Chill Chart

Source: National Oceanic and Atmospheric Administration (NOAA), National Weather Service

how the body loses heat

EVAPORATION: Heat loss in the form of vapor when body uses heat to evaporate moisture from skin surface (perspiration or “sweat”)

RESPIRATION: Heat loss from lungs’ warming inhaled cold air, which is then exhaled

How the Body Loses Heat


Heat loss from exposed body areas to the environment due to the difference between the temperature of the body and that of the cooler air (when air is <98.6°F)

CONVECTION:Heat loss from wind (blown air from fan, etc.) removing the layer of warm air next to the skin; rate of heat loss depends on wind/air speed


Heat loss through contact with a cooler object and transfer of heat to the cooler object; increases when in contact with cold wet objects (generally, conduction accounts for 2-3% of total heat loss in dry conditions; with wet clothes the loss is increased 5x, and rate of heat loss is 25x faster when a person is immersed in cold water)

how the body loses heat11

Each of these means of heat loss can play a large or small role in the development of a cold-related injury. In addition to air temperature, air movement (wind speed), and wetness, the skin surface area that is exposed to the cold is a factor in the amount of heat lost from the body.

How the Body Loses Heat
  • Factors in heat loss:
  • Air temperature, wind speed, wetness
  • Area of skin surface exposed to cold (particularly in radiation)
  • Contact with cold water or surfaces
how the body produces heat

Your body must produce an equal amount of heat to counter-balance the heat loss in order to survive and stay active in the cold. Heat is produced in the following ways:

How the Body Produces Heat
  • Metabolism: Biochemical reactions in the body which produce heat as a by-product
  • Physical Activity (exercise/work): Muscles produce most of the heat during physical work
  • Shivering: Inefficient quivering of the muscles that increases the body’s heat production; limited to a few hours because of depletion of muscle “fuel” stores and the onset of fatigue
how the body produces heat13

Factors influencing heat retention and tolerance to cold:

Factors important in heat production:

How the Body Produces Heat
  • Food intake
  • "Fuel" (glycogen) store
  • Fluid balance
  • Size and shape of the body (surface to volume ratio)
  • Layer of fat under the skin
  • Decreased blood flow through the skin and extremities
  • Insulation (clothing)
cold stress

If your body begins to lose heat faster than it is produced, your core body temperature drops below normal, and cold stress may result.

Cold Stress

Cold stress doesn’t only happen when conditions are below freezing; it can also be brought about by temperatures in the 50's coupled with some rain and wind.

how does cold affect work performance

Uncomfortably cold working conditions

(combination of temperature, wetness, wind)

How does cold affect work performance?


  • Immediate signs:
  • Decreased alertness
  • Restlessness, lack of concentration
  • Impaired performance of complex mental tasks
  • Impaired ability to perform manual tasks
  • Numbness, muscle weakness, stiffened joints
  • Lower work efficiency
  • Higheraccident rates
factors increasing risk of cold injuries illnesses

In general, people in good physical health are less susceptible to cold injury. In addition to weather conditions, the following factors may increase the risk of developing a cold injury:

Factors Increasing Risk of Cold Injuries/Illnesses
  • Previous cold-related injury
  • Predisposing health conditions::Cardiovascular disease, Diabetes, Anemia, Sickle cell disease, Vibration/White finger disease, other conditions associated with poor circulation, Hypertension, Asthma
  • Fatigue, poor physical condition
  • Poor nutrition
  • Medication: Anti-depressants, Sedatives, Tranquilizers, Others
  • Alcohol: Decreases awareness; impairs the body’s ability to regulate temperature and increases risk for hypothermia

Factors Increasing Risk of Cold Injuries/Illnesses (Con’t.)

  • Caffeine: Increases urine production, contributes to dehydration
  • Nicotine (Smoking): Increases risk for cold-induced skin injury (such as frostbite, immersion foot); promotes development of peripheral vascular disease
  • Wearing tight clothing: Restricts circulation
  • Under-activity: Can lead to decreased body heat production
  • Over-activity: Can lead to wet skin, clothing, or shoes from sweating
  • Under-dressing: Exposed fingers, nose, ears; uncovered head
  • Over-dressing: Can result in wet skin and clothing from sweating
  • Length of exposure
  • Age: Older adults may be at more risk than younger
  • Dehydration: Causes body’s natural defense mechanisms to fail and person becomes more susceptible to cold injuries
injuries illnesses from cold exposure

Working in freezing conditions or under prolonged exposures to temperatures above freezing, along with other factors, can cause cold-related injuries and illnesses, tissue damage, possible amputation, or death.

Injuries/Illnesses from Cold Exposure
  • Hypothermia is a serious medical emergency
  • Frostbite, frostnip, chilblains, and immersion injury most commonly affect the extremities - toes, fingers, ears, nose
injuries illnesses from cold exposure19
Injuries/Illnesses from Cold Exposure

The module “Cold-related Injuries and Illnesses” covers these topics at greater depth.

preventive measures
Preventive Measures

Planning: Plan for work in cold weather and implement controls to reduce and minimize exposure and the risk of cold stress.

  • Planning for the conditions
  • Engineering controls
  • Work practices
  • Appropriate clothing
  • Personal protective equipment

Training: Provide training in the recognition and treatment of cold-related injuries and illnesses. Supervisors, workers, and co-workers should watch for signs of cold stress and allow workers to interrupt their work if they are extremely uncomfortable.

Awareness: Being aware of how your body is reacting to the cold is important in preventing cold stress.


Monitor temperatures and air movement

  • Indoors: Take readings of temperature and air movement in all cold work areas at the start, middle, and end of each shift, at least every four hours.
  • Outdoors: The weather report can be used. Postpone work to a warmer day. Schedule heavy work during the warmer parts of the day if possible.
  • Where there is air movement from wind, ventilation, or travel in an open vehicle like a forklift, use the wind chill index to evaluate the hazard rather than the air temperature. The wind chill index takes into account the wind blowing the heat away from the body. If you know the temperature and speed of air movement, the wind chill can be looked up
  • in the wind chill chart.

Click to go to Wind Chill Chart on Slide #9

engineering controls
Engineering Controls
  • Use radiant heaters, warm air jets, and contact warm plates to warm workers.
  • Shield work areas from drafts or wind to reduce wind chill.
  • Provide heated warming shelters, e.g., tents, cabins, or rest rooms, for continuous work in temperatures below freezing.
  • Cover equipment handles, especially metal handles and bars, with thermal insulating material when temperatures drop below freezing (steel conducts heat away even faster than water).
  • Design machines and tools so that they can be operated without having to remove gloves or mittens.
  • In refrigerated rooms, minimize air speed as much as possible with properly designed air distribution systems. If workers are simultaneously exposed to vibration and/or toxic substances, reduced limits for cold exposure may be necessary.

Body: Wear at least three layers of loose-fitting clothing to trap air and provide insulation, and allow better ventilation.

  • Inner wicking layer made from polyester, polypropylene, or other synthetic material that draws moisture away from the skin and helps keep it dry.
  • Middle insulating layer made of wool, down, fleece, or other material with loft that will hold the body’s heat.

The following are recommendations to protect your body, hands, feet, and head when working in cold environments:

Outer layer for wind and water protection, made of “breathable” waterproof fabric that allows some ventilation (like Gortex® or nylon) and is windproof, and that may also need to be resistant to oil, fire, chemicals, or abrasion.

Any additional layer(s) of clothing should be large enough not to compress the inner layers and decrease the insulation properties.


Clothing (Con’t.)


Wear a wool knit cap or a liner under a hard hat to reduce excessive heat loss. A mask also helps protect the cheeks and nose. Up to 40% of body heat can be lost when the head is left exposed.


Clothing (Con’t.)

  • Hands: Wear gloves and mittens to prevent cold-related injuries as well as prevent accidents and maintain dexterity. The ACGIH* recommends wearing gloves when the air temperature is:
    • below 60.8°F for sedentary work
    • below 39.2°F for light work
    • below 19.4°F for moderate work
    • below 0°F, wear mittens, which protect better than gloves
  • Use glove/mitten liners for extraprotection.
  • Use fingerless gloves with mittensfor work requiring dexterity.

* The American Conference of Governmental Industrial Hygienists


Clothing (Con’t.)

  • Feet: Wear insulated boots with removable felt liners; remove liners daily for complete drying. Leather “mukluk” or “pack” type boots are porous, allowing the boots to "breathe" and letting perspiration evaporate.
    • If work involves standing in water or slush (e.g., fire fighting, farming), boots must be waterproof.
    • If there are crushing hazards, boots must be steel-toed.
  • Wear warm thick socks. If you wear two pairs of socks, inner liner socks made of polypropylene will help keep feet dry and warmer (silk, nylon, or thin wool will work also). Outer thicker socks should be larger so inner socks are not compressed.

Clothing (Con’t.)

  • (Socks, continued)
  • Make sure socks are not too thick; this may result in tightness and loss of insulating properties, and increase the risk for cold injuries. If the socks are too thin, the boots will fit loosely and may lead to blisters.
  • Change socks if they get wet or damp
  • Keep clothing dry. Remove snow and moisture from clothes prior to entering heated shelters. While resting in a heated area, remove outerwear to allow perspiration to evaporate.
  • Keep extra complete change of dry clothing, shoes, hat, gloves, etc., available in case work clothes become wet. The body loses heat faster if skin is in contact with wet clothing, and will chill rapidly. Excess perspiration will increase heat loss, so remove extra layers of clothing whenever you feel too warm.

General Guidelines

personal protective equipment
Personal Protective Equipment

Face and Eye Protection

  • In extremely cold conditions where face protection is needed, use eye protection that is separate from the nose and mouth to prevent fogging and frosting eye shields or glasses
  • Wear eye protection appropriate for the work
  • Wear eye protection that protects against:
    • ultraviolet light from the sun
    • glare from the snow
    • blowing snow/ice crystals
    • high wind chill conditions to protect the corneas of the eyes from potentially freezing
work practices

Pace the work to avoid excessive sweating. Change into dry clothes if clothes become wet. New employees should be given enough time to get acclimatized to cold and protective clothing before assuming a full work load.

  • Avoid sitting or standing still for prolonged periods.
  • Take frequent breaks, in shielded areas out of the cold, to avoid fatigue since energy is needed to keep muscles warm.
  • Work in pairs to keep an eye on each other and watch for signs of cold stress.
  • Consume warm, high calorie food such as pasta to maintain energy reserves. Working in the cold requires more energy to maintain body heat.
Work Practices

Work Practices are important preventive measures.

work practices30
Work Practices
  • Drink plenty of warm liquids often, especially when doing strenuous work, to prevent dehydration. Avoid caffeine, which increases urine production and contributes to dehydration. Avoid alcohol.
  • When it is cold, do not brush up against metal surfaces with bare skin. The skin may stick to it and get immediate frostbite.
  • Greases and oils get thick and hard which makes equipment difficult to use. Follow the proper procedures and use the right tools. Tools also get brittle in the cold, so use caution when working with them.
  • Avoid skin contact when handling evaporative liquids (gasoline, alcohol, cleaning fluids) while de-icing and fueling below 40°F. These materials in contact with the skin greatly increase heat loss from the body.
work practices31

American Conference of Governmental Industrial Hygienists (ACGIH)

Recommended Guidelines

Work Practices

The following slide shows the ACGIH’s recommendations for working in cold conditions. The exposure times are based on the wind chill factor. The work/break schedule applies to any four-hour period with moderate or heavy activity.

The warm-up break periods are of 10 minute duration in a warm location. The schedule assumes that "normal breaks" are taken once every two hours.

At the end of a 4-hour period, an extended break (e.g. lunch break) in a warm location is recommended.

More information is available in the ACGIH publications "2000 TLVs and BEIs" and "Documentation of TLVs and BEIs."

acgih recommended guidelines
ACGIH Recommended Guidelines

Table applies only if workers are wearing dry clothing and doing moderate to heavy work activity. For light to moderate work activity, move down one line to decrease maximum work period and increase the number of breaks.

*2007 TLVs and BEIs - Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati : American Conference of Governmental Industrial Hygienists (ACGIH), 2007 p. 202


Educate supervisors and workers on

    • symptoms of cold related disorders, and signs of cold stress to watch for
    • proper clothing habits
    • safe work practices
    • physical fitness requirements for work in cold
    • emergency procedures in case of cold injury
  • Allow workers to interrupt their work if they are extremely uncomfortable.
  • Supervisors should also ensure that work schedules allow appropriate rest periods. All of these measures should be incorporated into the relevant health and safety plans.

Training in recognition and treatment is important.

more information
More Information
  • LNI – DOSH – Cold Stress Videos
  • LNI-DOSH – Seasonal Safety Hazards
  • OSHA – Protecting workers in cold environments
  • NIOSH – Cold Stress