OSHA Heat Stress Training

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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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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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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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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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

[email protected]


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Documents

OSHA Heat Stress Training