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8/12/2019 OSHA Heat Stress Training
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8/12/2019 OSHA Heat Stress Training
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Glenn E. Lamson CIHOSHA Health Response Team
2012 OSHA Oil & Gas Safety Conference
Heat Stress:Defining, Evaluating and
Preventing
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Defining
Heat Stress
The net heat load that a worker is exposed to
from the combination of metabolic heat,
environmental factors and clothing Heat Strain
The bodys overall physiological response
from heat stress.
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Defining
Core Temperature Temperature of blood circulating around the
hypothalamus, aka the bodys thermostat
Best way to measure heat stress
370C or 98.60F
Equilibrium
Heat gain = heat loss
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Defining
Metabolic heat loss pathways Sweating (evaporative cooling)
Blood flow (radiant cooling)
Hormonal (regulation of salt & H2O balance) Anti-diuretic hormones reduce water and salt
losses through the kidneys
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Defining: Heat balance equation
S = (M-W) C R E
S is the change in the bodys heat content
(M-W) is metabolism minus the work being
performed and is always positive
Cis convective heat being exchanged
Ris radiant heat being exchanged
E
is evaporative heat loss and is always negative
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Defining: (M-W) Metabolism
Energy necessary to keep the body functioning and
accomplishing work
Estimated by oxygen consumption ~ 5 kcal/liter of O2
Metabolism is best derived from the table in the
ACGIHs TLVbooklet.
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Defining
CConvective heat loss or gain Heat transfer between skin and air
Function of air velocity
Skin temperature is 350C so C will be positive when
air temperature is over 350C
EEvaporative heat loss Perspiration evaporation causes body heat reduction
Function of air motion humidity If humidity is 100% E=zero
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Defining: RRadiant heat
Heat form electromagnetic radiation when itstrikes an object.
From skin and surrounding surfaces
DOES NOT heat the air it passes though Important in hot environments
and easily controlled
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Defining: Some rules of thumb
C: When ambient temp rises above skintemp, heat loss by convection is eliminated.
E: When humidity levels increase heat lossby evaporation is markedly reduced
As EH&S practitioners we have the mostcontrol over metabolism and radiant heat.
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Defining: Heat disorders
Heat stroke
Heat exhaustion
Heat syncope Heat cramps
Heat rash
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Defining: Heat disorders Heat Stroke
Heat stroke is the most serious heat-related disorder. Itoccurs when the body becomes unable to control its
temperature
The body's temperature rises rapidly, the sweating
mechanism fails, and the body is unable to cool down. When heat stroke occurs, the body temperature can rise
to 106 degrees Fahrenheit or higher within 10 to 15
minutes.
Heat stroke can cause death or permanent disability ifemergency treatment is not given.
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Defining: Heat disorders Heat Stroke
A medical emergency - call 911!
Symptoms
Hot, dry skin, hyperthermia, brain disorders
Treatment
Move the victim to a cool area
Cool body rapidly
Treat for shock
Transport to hospital
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Defining: Heat disorders Heat exhaustion
Heat exhaustion is the body's response toan excessive loss of the water and salt,
usually through excessive sweating.
Workers most prone to heat exhaustion
are those that are elderly, have high blood
pressure, and those working in a hotenvironment.
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Defining: Heat disorders Heat exhaustion
Symptoms Clammy moist skin usually with a raised
body temperature
Fatigue, weakness, nausea, headache,fainting
Treatment Remove from heat
Give fluids Fainting implies hospital visit
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Defining: Heat disorders Heat syncope
Fainting (syncope) episode or dizzinessthat usually occurs with prolonged
standing or sudden rising from a sitting or
lying position. Factors that may contribute to heat
syncope include dehydration and lack of
acclimatization.
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Defining: Heat disorders Heat syncope
Symptoms Light-headedness
Dizziness
Fainting
Treatment
Sit or lie down in a cool place at onset of
symptoms
Slowly drink water or a sports beverage
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Defining: Heat disorders Heat cramps
Muscle spasms caused by electrolyte loss
Symptoms: Muscle pains or spasms usually in the
abdomen, arms or legs
Treatment: Stop activity and sit in a cool place
Drink clear juice or a sports beverage Do NOT return to strenuous work for a few
hours after cramps subside
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Defining: Heat disorders Heat rash
AKA Prickly heat a skin irritation fromexcessive sweating
Symptoms:
red cluster of pimples or small blisters Most likely on the neck and upper chest,
groin, elbow crease and below breasts
Treatment: Keep the affected area dry
Dusting powders can increase comfort
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Evaluating: Measures of heat stress
Wet bulb globe temperature Traditional measure of heat stress, easy to
measure and basis for ACGIH TLV
Incorporates air temperature, radiant heat, air
movement and humidity Indoors
WBGT = 0.7tnwb+0.3tg
Outdoors (and indoors when there is a radiant heat source)
WBGT = 0.7tnwb+0.2tg+0.1tdb
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Evaluating: Wet bulb globe temperature
Forget that formula this is all you need
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Evaluating: Measures of metabolic rate
Work category Metabolic rate Work examples
Rest 115Sitting
Light 180Sitting, standing, light
arm/hand work
occasional walking
Moderate 300Normal walking,
moderate lifting
Heavy 415Heavy material handling
walking at a fast pace
Very Heavy 520Pick and shovel work
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Evaluating: Clothing effects
Clothing alters convective and evaporative
heat exchange
Insulating effects estimated using clothing
adjustment factors (CAFs)
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Evaluating: Clothing Adjustment Factors
CAFs are a function of clothing thickness
Work Clothes (long sleeves and pants) = 0
Coveralls (w/ only underwear under) = 0
Double-layer woven clothing = 3
Polyolefin coveralls = 1
Limited-use vapor-barrier coveralls = 11
Can not be added and do not apply to
completely encapsulating suits (level A)
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Evaluating: Applying CAFs to WBGTs
Once WBGT is calculated or measured
you need to adjust the value to the
workers dress level
Add the clothing adjustment factor to the
WBGT value (all values in C) provides the
Effective WBGT (WBGTeff)
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Evaluating: Acclimatization
Gradual physiological adaptation that improvesability to tolerate heat stress
Acquired by time lost even faster
Gained when working in heat 2 hours a day for 5 ofthe last 7 days to 10 of last 14 days
Loss begins when work in heat is discontinued.
Noticeable loss in 4 days, complete loss in 3-4 weeks.
Situations to monitor New hires Returning vacationers
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Evaluating: Tying all of that together
How to us all those calculations..
ACGIH TLV
WBGTeff Metabolic rate
Action Limit
Replaces unacclimatized TLV Work below action limit is presumed to be low
stress for any healthy worker
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Evaluating: Tying all of that together
Lets take an example... Joe is a 38 year welder who has been
working on a turnaround for 2 months
Joe wears jeans, a long sleeve shirt under a
pair of flame retardant coveralls
WBGT is 27 and it has been hot for a month
Calculation: WBGTeff= 27+3 or 30 Assuming that his work is moderate, using
the TLVhe should be further evaluated for
susceptibility for heat strain.
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Evaluating: Tying all of that together
Lets take a further look at that example... Variables:
Acclimatization
@ W=300 30
between TLV
& AL Metabolic work rate
TLVhas a ~ 30 between W=300 and W=415
CAF
CAF for double-layer woven clothing is 3
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Evaluating:
One more thing
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Evaluating: Measures of heat stress
NOAAs Heat index
A measure of how hot it
feels when the
amplifying effects of
increased humidity isfactored into the actual
air temperature.
Reported daily
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Evaluating: Measures of heat stress
Heat Index: Limitations
Developed for shady, light wind
conditions the heat index does
not take into account site
specific factors such as
metabolic work rate, radiant
heat, acclimatization or
clothing. Exposure to full
sunshine can increase the heat
index values by up to 15 F.
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Preventing: Safety & Health Plan
Heat injury safety and health plans
Essential after exceeding the TLV
Should be written and spell out controls
Anticipate Evaluate Control
Engineering Administrative PPE
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Preventing: Safety and Health Plan
Goal: Protect all workers from heat strain
Targets: workers over the AL and in PPE
Symptoms triggering action
Sustained HR >180 bbm age
Core temp >38.50C or 38.0C (unacclimatized)
Recovery HR >120 bbm
Sudden and severe fatigue, nausea, dizziness
or lightheadedness
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Preventing: Engineering Controls
Ventilation: removing the heat or adding
cooling
Shielding: protecting workers from radiant
heat waves
Important in processing plants
15 times the radiant temperature minus skin temp
SHADE!!!
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Preventing: Administrative Controls
Work-rest cycles
Shade
Proper hydration Acclimatization
Worker monitoring
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Preventing: Personal protective equipment
Cool vests
Vortex cooling suits
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Glenn E Lamson CIH
OSHA HRT
801-233-4914
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