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.

Session Objectives

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.

Body’s Cooling System

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.

The Heat Equation

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.

Additional Heat Stress Factors

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 heat-related stress? What about environments outside of work such as at home or with recreational activities during the hot months of the year?

Personal Sensitivity to Heat

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.

Heat Rash

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.

Fainting (Heat Syncope)

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?

Heat Cramps

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.

Heat Exhaustion

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.

Heatstroke

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.

Heat-Related Illness

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.

Heat Can Cause Accidents

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?

Engineering Controls

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.

Engineering Controls (cont.)

• 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?

Administrative Controls

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.

Administrative Controls (cont.)

• 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.

PPE

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?

Medical Surveillance

• 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.

Work Monitoring Programs

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?

Investigating Heat-Related Illness

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?

Preventing Heat-Related Illness

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.

Water, Water, Water

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.

Key Points To Remember

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 first-aid 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.