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					Heat Stress USA OSHA: 29CFR 1926.21 – Safety Training & Education 29CFR 1926.20 (a) – Unsafe Working Conditions 29CFR 1926.20(b) – Accident Reduction
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What is Heat Stress?
It is the buildup of heat in the body that can cause serious illness.

Learning Objectives
By the end of this course, you should be able to:
• Describe the causes of heat stress.

• Understand how you are at risk.
• Describe ways to prevent heat illness. • Identify the five major forms of heat illness. • Identify the warning signs of heat illness. • Identify what to do when symptoms are present.

It Won’t Happen to Me
If you think it won’t happen to you, consider this:
Since 1936, approximately 30,000 people have DIED from heat related illness. On the average, nearly 500 people die each year from heat related illness. Over 300 of those are from heat stroke.
Statistics from the National Safety Council

What Leads to Heat Stress?
There are two main ways in which our bodies produce heat:
Metabolic Heat – the body generates heat through the digestion of food, work, and exercise.

Environmental Heat – the body absorbs heat from the surrounding environment, whether it is the hot sun or a hot room.

What Leads to Heat Stress?
Some things to remember…
• Working or playing where it is hot puts stress on our body’s cooling system. • When the heat is combined with other stresses, such as hard physical work, loss of fluids, fatigue, or some medical conditions, it may lead to heat-related illness, disability, and even DEATH! • Weather and work conditions can lead to heat-related illness.

Our Bodies Try to Stay Cool
How we cope with heat…
• Your body is always generating heat and passing it to the environment. • If the air is moving (such as a fan or breeze), it is easier for your body to pass the heat to the environment.

• The harder your body is working, the more heat it has to lose.
• When the environment is hot and/or humid, or has a source of radiant heat (such as a furnace or sun), your body must work harder to get rid of its heat.

Our Bodies Try to Stay Cool
Our cooling system – there are three basic methods in which our bodies can be cooled
Convection – the transfer of heat through the circulation of air.

Evaporation – the process which occurs when a liquid changes into vapor (through sweating).

Radiation – heat is naturally emitted from the body surface.

Conditions Affecting the System
Acclimation – the biological process through which our bodies adapt to the environment – basically getting used to the heat.

Air Temperature – heat flows from warmer objects to cooler objects.
Air Movement – moving air speeds the evaporation process. Humidity – the amount of water vapor in the air affects the rate of evaporation. Clothing – the type of clothing affects the amount of heat our bodies absorb and retain, and can hinder evaporation.

When Your Body Overheats
When the body core temperature rises…
• Blood flow to the skin increases • Sweating increases • Heart rate increases to move blood – and heat – to the skin

When this works well, the core temperature drops or stabilizes at a safe level. When this does not work well, heat-related illness occurs.

When Your Body Overheats
What is the body core?
• The deep organs, especially heart, lungs, and other vital organs. • The arms, legs, and the tissues close to the skin are referred to as the periphery. • The core and the periphery compete with each other for blood supply.

The Heat Equation

High Temperature
+ High Humidity + Physical Work = Heat-Related Illness

Heat Index

Why Cooling Fails
So much sweat is lost that…
• dehydration occurs • the body cannot cool itself by sweating • the core temperature rises

Salt loss causes heat cramps So much of the blood flow goes to the skin that other organs cannot function properly

Risk Factors
• Overweight • Small body size • Skin disease • Liver, kidney, lung disease

• Poor nutrition
• Poor physical condition • Previous heat illness

• Pregnancy
• General fatigue, lack of sleep • Diarrhea, vomiting

• Lack of heat acclimatization
• Over 40 years of age • Diabetes • Heart disease, high blood pressure

• Dehydration
• Infections • Fever • Sunburn

More Risk Factors
• Recent immunization • Malnutrition

• Use of illegal drugs
• Low-salt diet • Sleeping pills • Excessive use of caffeine • Medications that limit or decrease sweating • Alcohol consumption during previous 24 hours

Risk Factors on the Job

• Heavy work
• Prolonged shifts • Heavy clothing • Protective gear and respirators • Exposure to any toxic agent

• Not enough water breaks

Heat Rash


Heat Cramps


Heat Exhaustion

Heat Stroke

• The more often you do hard work in the heat, the better your body becomes at keeping cool – think of it as cooling practice for your body. • If you are not used to working in the heat, you must take a week or two to get used to the heat (acclimated). • If you were ill or away from work for a week or so, you an lose your acclimation. • There are two ways to acclimate…

1. Limit Your Time - If you are experienced, keep your time in the hot environment to 50% of the shift on the first day. Increase to 80% the second day. You can work a full shift the third day. - If you are NOT experienced, keep your time in the hot environment to 20% on the first day. Increase your time to 40% the second day, 60% the third, 80% the fourth. The fifth day can be a full shift.

2. Limit Your Time –
Instead of reducing the exposure times to the hot job, you can become acclimated by reducing the physical demands of the job for a week or two.

• If you have heath problems or are not in good physical condition, you may need longer periods of acclimation. • When it is hot, first consider engineering and work practice controls to avoid heat related illness. • If you are taking any medication that increase your sensitivity to sunlight or hot environments, inform your supervisor immediately.

Maintain Body Fluids
• Fluid intake must be maintained throughout the course of physical activity.

• Do NOT rely on thirst as an indicator of dehydration because your body loses water faster than you realize. • Alcohol should be avoided because it is a diuretic, which increases dehydration and can interfere with heat loss.
• Ideally, you should drink one cup of water every 20 minutes when working in a hot environment.

Proper Diet
• Eat light during hot months.

• Avoid heavy foods – they increase metabolic heat production and also increase water loss.

• Eat smaller, well-balanced meals more often. • Eat foods that are high in water content, such as watermelon.

Rest Periods
• Pace your work activities during high temperatures. • Take frequent water breaks. • Take more frequent rest breaks in a shaded area. • If you feel symptoms of heat stress, take a break in an air conditioned area, including your car/truck.

• Wear lightweight, light-colored clothing to reflect heat and sunlight and help your body maintain normal temperatures. • Wear loose-fitting clothes that let air move over your body. • Wear wide-brimmed hats. • Wear long sleeves and pants to protect your skin from sunburn.

Engineering Controls
• Ensure inside areas have adequate ventilation and/or air cooling.

• Provide shaded awnings for outside work when possible.
• Use portable ventilation when possible. • Schedule non-essential tasks for cooler times of the day.

Engineering Controls
• Permit only acclimated workers to perform more strenuous tasks.

• Put more workers on a strenuous task so it is completed more quickly. • Provide air-conditioned rest areas, including cooled vehicles for those on the road.

Administrative Controls
• Increase frequency and lengths of water breaks during hot months.

• Provide cool drinking water near workers and remind them to drink one cup every 20 minutes.
• Train workers to prevent heat related illness and to recognize symptoms. • Train workers regarding the appropriate treatment for heat related illness. • Use relief workers.

Administrative Controls
• Use a “buddy system” since people are not likely to recognize (or may deny) their own symptoms. • Require workers to inform supervisors if they are pregnant or have a medical condition making them more sensitive to sunlight and/or hot environments. • Require workers to inform supervisors if they are taking any medication that cause sunlight or heat sensitivity. • Create heat exposure guidelines…

Sample of Heat Exposure Guidelines

NIOSH states that a good heat stress training program should include:
• Knowledge of the hazards of heat stress.
• Recognition of predisposing factors, danger signs, and symptoms. • Awareness of first-aid procedures for heat stroke.

• Employee responsibilities in avoiding heat stress.
• Use of protective clothing and equipment. • Dangers of using drugs, medication, alcohol, and caffeine in a hot work environment.

Verification of Knowledge
What is heat stress?
a. The body’s inability to sweat. b. A high temperature of the body during extreme heat conditions. c. The buildup of heat in the body that can cause serious illness.

d. The loss of salt in the body that can cause serious illness.

Verification of Knowledge
What are the two main ways in which our bodies produce heat?
a. Metabolic and Environmental Heat b. Metabolic and Radiant Heat c. Environmental and Evaporative Heat d. Convection and Environmental Heat

Verification of Knowledge
Which of the following is NOT a cause of heat stress?
a. Temperature b. Humidity c. Physical Work d. Air Movement Remember the equation: Temperature+Humidity+Physical Work = Heat Stress or Heat Related Illness

Verification of Knowledge
Which of the following is NOT a risk factor for heat stress?
a. Overweight
b. Alcohol within the last 24 hours c. Arthritis

d. Some prescription and non-prescription medications
e. Lack of heat acclimation

f. Diabetes
g. Caffeine

Verification of Knowledge
six hazards (illnesses) of heat stress.
a. Heat Rash

b. Sunburn
c. Heat Cramps

d. Fainting
e. Heat Exhaustion f. Heat Stroke

Verification of Knowledge
Which one of the following is a warning sign for potential heat illness?
a. Shaky hands
b. Drinking a lot of water c. Stops sweating d. Begins talking a lot

Verification of Knowledge
What should you do when symptoms are present (could be more than one)?
a. Remove clothing
b. Splash the person with water c. Make the person drink a lot of water d. Get for medical assistance e. Have person lie down f. Take the person’s shoes off

Verification of Knowledge
Ways to prevent heat illness
• •

Maintain Body Fluids Proper Diet


Frequent Rest Periods
Proper Clothing


Engineering Controls
Administrative Controls

Verification of Knowledge
How much water is recommended when working in the heat?
a. One gallon every hour
b. One gallon every two hours c. One cup every 30 minutes d. One cup every 20 minutes e. Two cups every 30 minutes f. As much as you can drink

Over the past hour or two, we have covered:
• The causes of heat stress.

• How you are at risk.
• Ways to prevent heat illness. • The five major forms of heat illness and their symptoms. • The warning signs of heat illness.

• What to do when symptoms are present.

Any Final Burning Questions?

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