You’re working hard and it’s hot. Your clothes are soaked with sweat.
You feel light-headed and you’re very thirsty. What you may not know is
that you could be suffering the first signs of heat stress.
Not only can working in hot conditions be uncomfortable, it can also be
hazardous if you don’t take the right precautions. You need to know
how to protect your health and safety when you work in hot conditions.
And that’s exactly what you’ll learn today.
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The main objectives of this session are to prepare you to work safely in
hot conditions and reduce the risk of heat-related illness. By the time this
session is over, you should be able to:
• Understand how hot conditions affect your body;
• Recognize symptoms of heat illness; and
• Take precautions to reduce the risk of heat illness.
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Let’s begin by talking about the body’s cooling system. Before we can
talk about heat-related illness and what to do about it, you need to
understand how your body attempts to cope with heat.
• Your body has a natural cooling system that is used to protect internal
organs from increases in temperature. When blood temperature
exceeds 98.6 degrees Fahrenheit (F), your heart rate increases and
blood circulates closer to the surface of the skin. This allows heat to
transfer out of the blood and into the cooler environment outside the
body. But this heat transfer is only effective if the temperature outside
the body is less than inside.
• If your body can’t lose enough heat by transferring heat out of the
bloodstream, your brain will signal the sweat glands to start sending
fluids to the surface of the skin.
• Once the sweat reaches the surface of the skin, the sweat will be
evaporated off the skin by the hot, dry environment outside the body.
The body’s heat will leave with the evaporated sweat.
But when humidity is high, the body’s cooling system isn’t very effective.
High heat prevents cooling through heat transfer out of the
bloodstream, and high humidity prevents sweat from evaporating. The
result can be heat-related illness.
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The Heat Equation is a simple way to determine the circumstances
under which the body’s cooling system could fail and you could face a
higher risk of heat illness.
• Basically, a work environment with high temperature and high
humidity where physical work is being performed is a prime breeding
ground for heat-related illness.
But as you’ll see in the next two slides, there are other factors that you
must also take into account besides the basic Heat Equation.
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In addition to temperature and humidity, you may also have to take into
account factors such as radiant heat and air velocity.
• Radiant heat has a significant impact on the amount of stress your
body could face in a given work environment. For example, working
around ovens, molten metals, furnaces, and other sources of high
heat adds to the effect of the temperature in the outside
environment, compounding the heat stress you face.
• Another important factor related to heat stress is air velocity. Stale,
stagnant air or a hot wind increase heat stress, whereas a cool breeze
reduces heat stress.
Think about your own work environment. Are you ever exposed to heatrelated stress? What about environments outside of work such as at
home or with recreational activities during the hot months of the year?
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Along with environmental factors that tend to increase the potential for
heat-related stress and illness, you also have to take into account your
own sensitivity to heat. There are a number of factors that affect your
sensitivity to heat.
• Acclimatization, or getting used to heat, is a very important factor. The
body can take 7 to14 days to condition itself to working in the heat. If
you’re not used to it, you’re much more susceptible to heat-related
illness.
• Age is also a factor. Older workers are often at greater risk than
younger workers.
• People who are overweight, are pregnant, have had inadequate rest,
or are just physically unfit are more likely to be affected by heat stress,
as is a person who is sick.
• People have different rates of metabolism. Those who sweat at a
higher rate are less susceptible to heat stress.
• Finally, consuming too much alcohol after work contributes to
dehydration and can affect the way a person’s body responds to
working in hot conditions the next day.
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Now let’s turn our attention to the different kinds of heat-related illness.
Heat rash is the least severe of the heat-related illnesses. But although it’s
only a minor health problem, heat rash can be very uncomfortable.
• Heat rash typically occurs in hot and humid environments where the
sweat can’t evaporate off the body.
• Heat rash symptoms include a red, bumpy rash that often itches.
Scratching the rash may cause further complications if scratched skin
becomes infected due to exposure to dust and dirt.
• Itching related to heat rash can sometimes make sleeping difficult,
too.
• Heat rash can be prevented by taking regular breaks in a cool place
when it’s very hot and humid so that your body stops sweating for a
while. Keeping your skin as dry and clean as possible also helps
prevent or treat heat rash.
If you’ve ever had heat rash, you know how uncomfortable it can be.
That’s why it’s wise to take preventive measures.
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Another relatively minor type of heat-related illness is called heat
syncope, better known as fainting.
• Fainting generally occurs when a person has not yet become used to
or acclimated to working in a hot environment.
• It also usually happens when someone is doing a job that doesn’t
require much movement and is just standing still in the heat most the
time.
• What happens then is that the blood pools in the legs, which reduces
the amount of blood that goes to the brain. This results in fainting.
• You can usually recover quickly from a fainting spell by lying down in a
cool, shady area for a while with legs slightly raised.
• Fainting in hot weather can be prevented by moving around a little,
rather than standing still for long periods. Moving around helps
maintain adequate blood volume in your brain.
Have you ever fainted or seen someone faint in hot conditions?
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A more severe form of heat-related illness is known as heat cramps.
• Heat cramps are painful muscle cramps. Tired muscles are the most
susceptible. So if you’re not in good physical shape or are not used to
the work, you’re more susceptible to heat cramps.
• Heat cramps are usually caused when the body’s salt, which is lost by
sweating, is not replaced. Drinking water will replace the liquid that
your body loses but may not adequately replace the salt that was lost.
• Drinking electrolyte liquids such as sports drinks can help prevent or
treat heat cramps.
• Severe cases of heat cramps may require a visit to the doctor, who will
use an intravenous saline solution to replace salt.
Have you ever experienced heat cramps? If you have, you know that
they can be painful. Fortunately, they are usually pretty easy to treat.
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Now we’ll discuss the really serious heat-related illnesses.
• Heat exhaustion, the second most-serious type of heat illness, is the
result of loss of fluid or salt, or both, through sweating. The victim does
not take in enough liquids and electrolyte solutions when working to
maintain adequate levels of fluid and salt.
• Symptoms of heat exhaustion include weakness, dizziness, and
nausea.
• The victim’s skin feels clammy and the complexion is pale or flushed.
Body temperature may also be above normal.
• Treatment for heat exhaustion includes resting in a cool place and
drinking electrolyte fluids. You should also loosen or remove heavy
clothing and try to cool victims by fanning them, spraying them with a
cool mist of water, or applying a cool, wet cloth.
• Severe cases of heat exhaustion may result in vomiting or loss of
consciousness. Call for emergency assistance immediately if first-aid
treatment does not help and a victim starts vomiting or loses
consciousness. Remember that severe cases of heat exhaustion can
advance quickly to heatstroke. So don’t hesitate to call for medical
assistance.
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Heatstroke is the most serious type of heat illness.
• It occurs when the body’s natural cooling mechanism stops
functioning and the victim stops sweating. Body temperature may
reach 104F or higher.
• Symptoms of heatstroke include very hot and dry skin.
• The victim will also become confused or delirious and may begin to
suffer convulsions or seizures, and collapse or lose consciousness.
• Without immediate medical treatment, a victim could die. Call for an
ambulance as soon as you notice symptoms of heatstroke.
• While waiting for help to arrive, move the victim to a cool spot. If the
victim is conscious, provide plenty of fluids. Never give liquids to an
unconscious person. Remove any heavy outer clothing. Keep the
victim cool by soaking clothing with cool water or spraying with mists
of water. If ice packs are available, place them under the victim’s
armpits and in the groin area. Fanning will also help.
Remember that heatstroke is a life threatening illness and that untreated
heat exhaustion can quickly lead to heatstroke.
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Now it’s time to ask yourself if you understand the information that has
been presented so far. Do you understand what we’ve discussed about
the risk and treatment of heat-related illness on the job?
Understanding this information is important to your health and will allow
you to work more safely in hot conditions.
Now let’s continue to the next slide and talk about how hot conditions
can affect your safety as well as your health. And then we’ll go on to
talk about what we are doing to help protect you from heat-related
illness and accidents.
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Working in hot conditions can not only cause heat-related illness, if
you’re not careful, it can also cause accidents on the job.
• Because heat affects the body’s cooling system and reduces blood
flow to the brain, muscles, and other organs, you can experience a
decrease in strength and an increase in fatigue. Fatigue can result in
inattentiveness to job hazards and slow responses in emergencies.
• Heat can also reduce your ability to understand instructions or retain
information. Even a short-term reduction in mental sharpness could
result in an accident if you haven’t made a correct or safe decision
when dealing with a job or task.
• And don’t forget that heat usually makes people uncomfortable and
irritable. This can cause a worker to become easily frustrated, cut
corners, or ignore safety procedures. This type of behavior is an open
invitation to an accident.
• There are also other risks caused by heat that can contribute to
accidents. For example, sweaty hands can drop tools or fogged-up
safety glasses can cause you to trip and fall.
Can you think of other ways heat might increase the risk of accidents?
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As you can see, working in hot conditions can be hazardous for many
different reasons. One way to deal with hot conditions in the workplace
and reduce the risk of heat-related illness and accidents is to use
engineering controls.
• One of the prime controls used to reduce heat in the workplace is
general ventilation. For example, ventilation might include removing
heat from the building with exhaust fans or blowing air through the
building to create a crosswind that reduces the heat stress by
improving air velocity.
• Spot cooling can also be used, such as providing an exhaust system
for a specific heat source like an oven or melting pot. Spot cooling
removes the heat before it reaches nearby workers. Another example
of spot cooling is focused air-conditioning, which blows cool air over a
workstation or area where a worker will be stationed throughout the
day. Even outdoor workers can benefit from spot cooling by using a
fan and water mist system like the ones used by professional football
teams during summer practice sessions.
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• Shielding workers from radiant heat sources is another way to control
heat stress. For example, workers and workstations might be located
inside an air-conditioned control room. Heat-resistant shields might be
installed around ovens or melting pots. Workers can stand behind the
shields while observing the equipment. Outdoor workers might be
provided with tent-like devices that shade them from the radiant heat
of the sun.
• Whenever possible, machinery can also be used so that workers don’t
have to use manual methods that put more stress on the body. For
example, in hot work environments employees might control machine
operations from inside a cool control booth, thus greatly reducing the
risk of heat-related illness.
Can you think of some engineering controls used in your work area to
protect you from excessive heat?
15
Administrative controls are also used to help protect workers from heat
stress.
• For example, heavy work—particularly work that requires workers to
wear a lot of hot personal protective equipment (PPE)—might be
scheduled for cooler times of the year or cooler times of the day, like
evening or early morning.
• More frequent breaks might be allowed, or breaks might be extended
so that workers can rest away from hot conditions for longer periods.
For example, in very high temperatures, with high humidity, a
demanding level of work, and a lot of heavy PPE, workers might be
required to take a short break every hour or so to prevent heat-related
illness.
• Another administrative control to prevent heat stress is to allow workers
sufficient time to become conditioned to working in hot conditions.
Remember that it can take 7 to 14 days to become acclimatized to
hot conditions. As a result, new employees or those returning from
vacation might be exposed to a hot environment for short periods at
first, gradually increasing the length of exposure over the course of a
week or so.
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• Reducing the physical demands on workers who are exposed to high
temperatures and high humidity is also an effective way to reduce
heat stress. For example, production requirements might be reduced
or work schedules might be rearranged to allow workers sufficient rest
time.
• Having relief workers on hand to fill in while another crew rests in a
cool recovery area is another effective way to reduce heat stress and
protect workers from heat illness.
• In some cases, companies might limit the number of hours employees
work in a hot environment each workday.
• And workers will be encouraged to pace themselves, being careful
not to overexert.
Think of the administrative controls designed to protect you from
excessive heat.
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Another important step that can be taken to reduce heat stress risks is to
use PPE that has been designed specially for hot conditions. For
example:
• Light hats that provide shade for the head, face, and neck when
working outdoors;
• Portable water products that can be worn on the back or around the
waist and accessed through a straw or tube system to provide
adequate fluids;
• Reflective clothing that reduces the impact of radiant heat; or
• Systems that circulate air around the body, such as those used with
full-body suits with air-supplied breathing systems.
Are you familiar with any special PPE used by employees who work in
hot conditions?
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• Periodic medical evaluations performed on employees who regularly
work in hot environments can also help reduce the risk of heat-related
illness.
• A medical evaluation determines if a worker is at risk of developing
heat-related illness. High-risk employees may include those with at-risk
medical conditions or those taking certain prescription medicines.
• High-risk employees need to be removed from jobs in hot working
environments for their own safety.
Think about the risk factors we’ve discussed. Could you possibly be in a
high-risk group? If so, you should speak to your doctor and your
supervisor.
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Some workplaces also use worker monitoring programs to check on
high-risk employees during the workday.
• For example, a worker’s heart rate is checked at the beginning of a
rest period. If the worker’s pulse is greater than 110 beats per minute,
the next work period is shortened by a third.
• Pulse is checked again 2.5 minutes into the break to determine
recovery rate. The difference between the heart rate at the beginning
of the break and 2.5 minutes later should be greater than 10 beats per
minute. If not, the body may not be recovering adequately, and the
worker needs to watch for other signs of heat-related illness.
• Body temperature might also be monitored. Body temperature taken
orally at the end of the day before drinking water should not exceed
99.7F. If it does, the next day’s work cycle should be shortened by a
third for that employee.
• Finally, water loss can be measured by weighing workers before and
after each shift. Weight loss during a single day should not exceed 1.5
percent of a worker’s total weight. If it does, the worker must be
careful to drink more fluids the next day.
Are you familiar with monitoring programs designed to protect workers
at high risk of heat stress on the job?
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When all our programs and strategies to prevent heat-related illness fail
and a worker succumbs to heat stress, we investigate the incident to
determine what happened so that we can prevent another
occurrence. When investigating heat-related incidents, we look at
things such as:
• Events leading up to the incident—temperature, humidity, ventilation
and air circulation, and sources of radiant heat;
• Work being done at the time of the incident—light, medium, or heavy;
• Length of time the employee was working before the incident—for
example, days in a row worker had been doing the job, time of last
break, and whether worker was properly acclimatized;
• Type of engineering and administrative controls being used;
• Type of PPE being worn; and
• Medical surveillance and worker monitoring that had been done prior
to the incident.
Can you think of any other issues that should be examined during an
investigation of a heat-related incident?
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Now it’s time to ask yourself if you understand the information presented
in the previous slides. Do you understand what we’ve discussed about
ways to prevent heat-related illness on the job?
It’s important that you understand this information so that you can use it
to protect yourself against heat stress.
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The importance of drinking enough fluids cannot be overemphasized
when you work in hot conditions. Your body expels a great amount of
fluid and salt when you work hard and sweat a lot. This fluid and salt
must be replaced in order to prevent heat-related illness.
• So drink plenty of water all day.
• Drink electrolyte-balanced fluids such as sports drinks to help replace
the salt that is lost through heavy sweating.
• Experts recommend drinking at least one cup—that’s about
8 ounces—of fluids every 15 to 20 minutes when working in hot
conditions.
• They also suggest that you avoid drinking caffeinated beverages such
as coffee and some sodas when you work in hot conditions. And they
advise you to go light or avoid alcohol after work. Caffeine and
alcohol both contribute to loss of body water, which prevents your
body from recovering properly from heat stress and increases the risk
of heat-related illness.
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Here are the main points to remember from this session on working in hot
conditions:
• Working in hot conditions can affect your health and safety.
• Make sure you understand the risks and the precautions you have to
take to prevent problems.
• Know the symptoms of heat-related illness and the appropriate firstaid response for different degrees of heat stress.
• Use all available measures to reduce heat stress and keep safe and
healthy when working in hot conditions.
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