Space heaters, shelters, hand/foot warmers reduce cold stress and the risk of hypothermia, frostbite, and other cold-related injuries.
Hazard Analysis — Cold-related Injuries and Illnesses
Workers who build or install roof trusses in cold environments face hazards from cold-related injuries and illnesses including slipping and falling, hypothermia, and frostbite. Working in cold temperatures, especially with wind and moist clothing, poses a serious threat to a worker’s health. Prolonged periods of exposure to harsh conditions can result in injuries, usually starting with a worker’s extremities.
Workers exposed to cold temperatures face the hazards of falls, frostbite, and hypothermia if not properly prepared. The rate of injuries resulting from slips and falls increases as the temperature falls below freezing. Cold temperatures combined with wind and/or moisture cause the body to lose heat at a higher rate and increases its susceptibility to cold-related injuries and illnesses.
Working in cold environments increases a worker’s chances of suffering a cold-related injury or illness. Cold-related health problems can range from mild frostbite or bruising to death from severe hypothermia or head injuries from falling.
- Frostbite is a cold-related injury that usually affects the body’s extremities and exposed skin. The freezing of underlying tissues and skin results in frostbite. A worker's hands, feet, nose, and ears face the greatest risk of injury. If severe, amputation may be the only form of treatment. Symptoms may include developing gray or white patches (blisters in severe cases) on reddened skin and feeling numb or hard in affected areas. Workers experiencing frostbite should seek medical attention immediately. If not available, begin first aid by relocating the worker to a warm location, removing wet any clothing, and gently warming the affected area. Soak the affected areas in warm (never hot) water or keep applying warm cloths to affected ears, nose or cheeks for 20 to 30 minutes. Warming is complete when the skin is soft and sensation returns. Apply dry, sterile dressings to the frostbitten areas. Put dressings between frostbitten fingers or toes to keep them separated. If the frostbite is extensive, give warm drinks to the person in order to replace lost fluids. Do not use direct dry heat (such as a radiator, campfire, heating pad, or hair dryer) or hot water and do not rub the skin. Once frostbitten skin has been warmed it must not be returned to the cold or further damage may occur. (Source: Medline Plus from NIH, Accessed 3-14-14, http://www.nlm.nih.gov/medlineplus/ency/article/000057.htm)
Grade IV Frostbite
- Hypothermia occurs when the body’s core temperature drops from its normal temperature of 98.6ºF to less than 95ºF. The body is losing heat at a faster rate than it can generate it. Hypothermia most frequently occurs at temperatures below 40ºF but can occur at warmer temperatures if wind and moisture are present. Symptoms of hypothermia may include shivering, pale skin, slow or slurred speech, loss of coordination, slowed or shallow breathing, and loss of consciousness. Hypothermia is a life threatening injury that must be treated with medical attention immediately.
In a 2010 article written by Princeton University’s Rick Curtis, the stages of hypothermia are broken down by core temperature in addition to the signs and symptoms observed during each stage.
Signs & Symptoms
99 - 97ºF
Normal, shivering can begin
97 - 95ºF
Cold sensation, goose bumps, unable to perform complex tasks with hands, shiver can be mild to severe, hands numb
95 - 93ºF
Shivering, intense, muscle incoordination becomes apparent, movements slow and labored, stumbling pace, mild confusion, may appear alert. Use sobriety test, if unable to walk a 30 foot straight line, the person is hypothermic.
93 - 90ºF
Violent shivering persists, difficulty speaking, sluggish thinking, amnesia starts to appear, gross muscle movements sluggish, unable to use hands, stumbles frequently, difficulty speaking, signs of depression, withdrawn.
90 - 86ºF
Shivering stops, exposed skin blue of puffy, muscle coordination very poor, inability to walk, confusion, incoherent/irrational behavior, but may be able to maintain posture and appearance of awareness
86 - 82ºF
Muscle rigidity, semiconscious, stupor, loss of awareness of others, pulse and respiration rate decrease, possible heart fibrillation
82 - 78ºF
Unconscious, heart beat and respiration erratic, pulse may not be palpable
78 - 75ºF
Pulmonary edema, cardiac and respiratory failure, death. Death may occur before this temperature is reached.
Level of Risk:
In construction, working in cold environments is inevitable. According to CPWR, “nearly all production occupations in construction require working in very hot or very cold temperatures at least once a month, with almost half (44%) exposed weekly (chart 34f). Roofers, power-line installers, and ironworkers are exposed to extreme temperatures more frequently than other construction occupations (CPWR Construction Chart Book, Fifth Edition, 2013, p. 85).” Chart 34f, depicting the percentage of workers exposed to very hot or cold conditions at least weekly, monthly, and yearly is displayed below.
(CPWR Construction Chart Book, Fifth Edition, p. 86)
Chart 44f from CPWR's Construction Chart Book shows that 39.5 percent of the 18,130, approximately 7,000, nonfatal injuries from falls that occured inconstruction in 2010 were the result of a fall on the same level. Working in a cold environment likely contributed to some of these injuries but the number is not known.
(CPWR Construction Chart Book, Fifth Edition, p. 106)
OSHA, state agencies and private studies have shown that working in the cold environments increases a worker’s risk for cold-related injury and illness. Dr. Juhani Hassi has shown that as temperatures fall below 29°F, cold exposure injury rates increase (Hassi, 2000). Risks can be reduced through the use of a cold stress program, engineering controls and personal protective equipment.
The level of risk of cold-related injuries and illnesses depends on the following:
- Temperature and wind speed of the work environment.
- Exposure to water or evaporative liquids.
- A worker’s ability to acclimate to the cold environment. Workers not accustomed to the cold should be given more frequent breaks in warm up areas until their bodies build up a tolerance to the conditions.
- Amount and type of protective clothing equipment a worker is wearing. Workers who do not wear a minimum of three layers of loose fitting clothing and limit bare skin exposure are at increased risk of hypothermia. Inner layers should be materials such as wool or synthetics that remain good insulators when wet. Outer layers should be wind proof and repel moisture.
- Access to warm-up areas. The American Conference of Governmental Industrial Hygienists (ACGIH) provides a warm-up schedule to prevent workers from working extended periods of time without a break in a warm area.
- Access to warm sweet liquids. Warm liquids help to raise the body core temperature.
- Maintenance of walking and working surfaces and traction between surfaces and footwear.
Construction Chart Book
CPWR – The Center for Construction Research and Training: The Construction Chart Book. Silver Spring, Fifth Edition, Maryland. 2013, p.85-86, 106.
American Journal of Industrial Medicine
Hassi, J., Gardner, L., Hendricks, S. and Bell, J. (2000), Occupational injuries in the mining industry and their association with statewide cold ambient temperatures in the USA. Am. J. Ind. Med., 38: 49–58. doi: 10.1002/1097-0274(200007)38:1<49::AID-AJIM6>3.0.CO;2-3
OSHA Cold Stress
"Cold Stress Guide." Occupational Safety and Health Administration. Web. 30 January 2014. https://www.osha.gov/SLTC/emergencypreparedness/guides/cold.html
When working in cold environments, employers and workers must consider factors such as air temperature, wind, and moisture. Protective clothing and equipment, engineering controls, and administrative controls should be considered to control the risk of cold-related injuries and illnesses.
Identifying situations that could require workers to perform tasks in cold weather conditions should be a key part of the site safety planning process.
To determine if workers are at risk of cold-related injuries and illnesses consider the following:
What is the air temperature the workers will be exposed to?
- Temperature should be measured and recorded at least every 4 hours when below 30.2°F.
- Will walking or working surfaces be covered in ice or snow?
What is the wind speed in the work area?
- Wind speed should be measured at least every 4 hours when working indoors with wind speeds greater than 5 mph.
- Wind speed should be measured every 4 hours when working outdoors in temperatures below 30.2°F.
- Will workers use toxic substances or be exposed to vibration?
- Will workers use gasoline, alcohol, or other liquids that evaporate quickly?
- Will workers be exposed to direct sun or be working in an enclosed area?
- Will workers be submerged in water or face the possibility of their clothing becoming wet?
- Is a place to warm-up readily available?
- Will warm sweet liquids be readily available?
- Do workers have health conditions or take medications that reduce their ability to regulate body temperature?
- Are workers medically certified to work in cold environments?
- Does the equipment used by the workers contribute to their cold stress?
- Will workers be contacting cold surfaces such as metal?
- Does the required personal protective equipment have the potential to raise a worker’s body temperature?
- Will the required work rate cause workers to sweat heavily resulting in wet clothing?
- Can equipment or scheduling be used to reduce the work that must be performed in cold environments?
When evaluating the severity of conditions, employers and workers should consider wind chill in addition to air temperature. The American Conference of Government Industrial Hygienists (ACGIH) chart on equivalent chill temperature provides a more accurate representation of the how cold an environment will actually feel due to wind. In addition, heat loss can be significantly increased if moisture is present.
Regulations & Standards:
The ACGIH provides Threshold Limit Values (TLVs) for working in cold weather. The TLVs consider air temperatures combined with wind to determine the maximum work period without a warm up break during a four-hour shift. The TLVs apply to workers who are adequately dressed for the present conditions.
With permission from ACGIH®: 2013 TLVs® and BEIs® Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: ACGIH, 2013, p. 202.
Wind greatly increases the effects of cold temperatures. The ACGIH developed a table to show the equivalent chill temperature and effect on bare skin for different combinations of wind speed and temperature.
With permission from ACGIH®: 2013 TLVs® and BEIs® Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: ACGIH, 2013, p. 199.
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.
Engineering controls, personal protective clothing and equipment, and cold stress prevention programs all aid in protecting workers from hazardous conditions. Many state agencies provide information and recommendations for working in the cold safely and preventing cold-related illness and injuries. Below is a list of resources workers should consult for additional information on working in cold environments.
Alaska Department of Labor
New Jersey Department of Health
Washington State Department of Labor & Industries
Taylor Kingston and Michael R. Cooper - Aria Environmental, Inc.
Bruce Lippy - CPWR
BIM is a concept that offers software application to integrate building information for hazard identification and safety planning.
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