Transcript Working in Cold Environments Preventing Cold-related Injuries and Illnesses January, 2011

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
See the module “Cold-related Injuries and Illnesses” for more detailed
descriptions of hypothermia, frostbite, and other cold injuries.
Introduction
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 coldrelated 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:
 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
• Window cleaning
• Police, fire, and emergency
response
• Postal, delivery services
• Sanitation/trash collecting
• Utilities, communications
Maintaining Temperature: Balancing
Heat Loss and Heat Production
Most of the body’s energy
is
maintain
an
Theused
body to
does
this through
Normal
internal (core)
balancing
heat lossbody
and
core body
temperature:
heat
production.
temperature of
98.6°F
approximately 98.6°F
(37°C)
In cold conditions, the body
(37°C).
reduces heat loss and
increases heat production.
Body’s core area:
(internal organs,
especially ones
vital for survival)
•
•
•
•
•
Heart
Brain
Lungs
Liver
Kidneys
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
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 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.
Wind Chill Chart
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.
Source: National Oceanic and Atmospheric Administration (NOAA), National Weather Service
How the Body Loses Heat
EVAPORATION:
RESPIRATION:
Heat loss in the form
of vapor when body
uses heat to
evaporate moisture
from skin surface
(perspiration or
“sweat”)
Heat loss from lungs’
warming inhaled cold
air, which is then
exhaled
RADIATION:
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
CONDUCTION:
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 Heat
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.
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:
• 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 Heat
Factors important in heat
production:
• Food intake
Factors influencing heat
retention and tolerance to
cold:
• "Fuel" (glycogen) store
• Size and shape of the body
(surface to volume ratio)
• Fluid balance
• 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 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)
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
► Higher
accident 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:
• 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.
• 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 Exposure
Injury/Illness
Hypothermia
Cause
Occurs when core body temperature decreases to below
95°F; can occur in air temperatures below or above
freezing (or water temperatures ; serious medical
emergency, can be fatal
Frostbite
Ice crystal formation in skin and other tissues of the body at
or below freezing (32°F); causes permanent damage and
destruction to blood vessels and other structures, can result
in amputation
Frostnip
Ice crystal formation only in the very outer layer of the skin;
causes no permanent damage
Chilblains
Mild cold injury due to prolonged and repeated exposure for
several hours to temperatures above freezing (32°F to
60°F); affected skin is swollen, red, tingly, painful, and itchy
Immersion injury
(Trench foot)
Exposure of wet feet (or hands, other body areas) to cold
temperatures over hours to days at or above freezing (32°F
to 50°F); damages nerves and muscles; can cause
permanent damage
The module “Cold-related Injuries and Illnesses” covers these topics at greater depth.
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 coldrelated 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.
Planning
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
Click to go to Wind Chill
in the wind chill chart.
Chart on Slide #9
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.
Clothing
The following are recommendations to protect your body, hands, feet, and
head when working in cold environments:
• Body: Wear at least three layers of loose-fitting clothing to trap air
and provide insulation, and allow better ventilation.
1. Inner wicking layer made from polyester,
polypropylene, or other synthetic material
that draws moisture away from the skin
and helps keep it dry.
2. Middle insulating layer made of wool, down,
fleece, or other material with loft that will
hold the body’s heat.
3. 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.)
Head:
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 extra
protection.
Use fingerless gloves with mittens
for 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
General Guidelines
 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.
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
clothesWork
if clothes
becomeare
wet.important
New employees
should be
Practices
preventive
given enough time to getmeasures.
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
 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 Practices
American Conference of Governmental Industrial Hygienists (ACGIH)
Recommended Guidelines
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
TLVs Work/Warm-up Schedule for Outside Workers based on a Four-Hour Shift*
Air Temperature - No Noticeable
Sunny Sky
Wind
°C
°F
(approx) (approx)
Max.
work
Period
No. of
Breaks
**
5 mph Wind
Max.
Work
Period
No. of
Breaks
-26° to
-28°
-15° to
-19°
(Norm breaks) 1 (Norm breaks) 1
-29°to 31°
-20°to
-24°
(Norm breaks) 1
-32° to
-34°
-25°to
-29°
75
min.
-35° to
-37°
-30° to
-34°
-38° to
-39°
10 mph Wind
15 mph Wind
20 mph Wind
Max.
Work
Period
No. of
Breaks
Max.
Work
Period
No. of
Breaks
Max.
Work
Period
No. of
Breaks
75
min.
2
55
min.
3
40
min.
4
30
min.
5
75
min.
2
55
min.
3
40
min.
4
2
55
min.
3
40
min.
4
30
min.
5
55
min.
3
40
min.
4
30
min.
5
-35° to
-39°
40
min.
4
30
min.
5
-40° to
-42°
-40°to
-44°
30
min.
5
-43° &
below
-45° &
below
Non-emergency
work should
cease
Non-emergency
work should
cease
Non-emergency
work should
cease
Non-emergency
work should
cease
Non-emergency
work should
cease
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
Training
• Training
Educate supervisors
and workers
on
in recognition
and treatment
is important.
– 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.
More Information
 LNI – DOSH – Cold Stress Videos
 LNI-DOSH – Seasonal Safety Hazards
 OSHA – Protecting workers in cold environments
 NIOSH – Cold Stress