Treating All Workers the Same in the Heat? That Could Be Risky

Treating All Workers the Same in the Heat? That Could Be Risky


Read the full Reuseable Packaging news article, “Treating All Workers the Same in the Heat? That Could Be Risky” featured here.

By Nicole Moyen, Vice President of Research and Development at Kenzen and heat stress blogger

When it comes to planning for the prevention of heat-related injuries & illnesses among an entire workforce, a one-size plan does not fit all.

The research behind managing worker safety under hot working conditions has largely been based on studies of young, healthy men, which means that other populations – women, older adults, and people with other risk factors – will need different accommodations if a heat safety program is to be effective.

Sex, age, health status, and other factors can impact risk

According to researchers who study how heat affects workforces, “…existing guidelines adopted and recommended for use by government agencies worldwide to protect the public and workers also assumes a “one size fits all” approach to protect human health. These guidelines generally prescribe protective measures (e.g., heat advisories, exposure limits) using models defined by the assessment of heat strain in young and/or relatively healthy adults. They fail to consider key factors such as sex, age, health status, and other factors, which can markedly alter a person’s tolerance to heat, thereby leaving a large segment of the population under-protected…” (1)

For example, a man working at the same relative work rate as a woman will typically have a higher sweat rate. This is because men generally have a larger body-surface-area-to-mass ratio than women.

Given that sweating is the main way a body gets rid of body heat, this higher sweat rate among men means that their body temperature will be lower in hot-dry (low humidity) climates. As a result of this higher sweat rate & lower body temperature, men will likely be able to work for a longer period of time than women. However, in hot-humid climates where sweat can’t evaporate as easily and therefore doesn’t cool you down, women will likely be able to work for a longer period of time than men. This is because men will continue to sweat more than women, but this sweat won’t be cooling them down, and in fact, they’ll just lose a lot of body water. The effect: in hot-humid environments, men will become dehydrated more quickly than women, and see a faster increase in core body temperature – the primary trigger of heat-related injuries and illnesses.

Older workers more susceptible to heat stress

Another natural factor that can vary the susceptibility of heat-related injuries and illnesses among workers is age. After age 35, the body’s ability to dissipate heat, primarily through sweating, declines. As a result, older adults tend to have higher core body temperatures than younger adults, when working at the same rate in the heat. This difference between older and younger individuals can be minimized with heat acclimatization and endurance training.

In addition, some people are able to acclimatize faster and tolerate heat better than others; a portion of this appears to be attributable to genetic makeup.

Moreover, there are various diseases that can impair the body’s ability to effectively thermoregulate, such as various cardiovascular diseases (e.g., hypertension), sweat gland disorders (e.g., Type I and Type II diabetes), skin disorders (e.g., psoriasis), and metabolic disorders. Individuals with these diseases will be at increased risk for heat-related injuries and illnesses.

These factors (age, biological sex, and disease) affect each individual differently when working in the heat, and therefore require workforce supervisors to alter their approach in developing work/rest schedules for workers. It is important to observe changes in employees’ health while on the job site and take appropriate, individualized measures to ensure that each person remains at safe core body temperatures. Always listen to workers when they say they’re not feeling well, and allow them to take a break.

Smart PPE sensors can detect and relay warnings

Smart personal protective equipment (PPE) is available to monitor individual workers’ health during work in the heat. New sensors, worn on the body, can detect and relay warnings to both the worker and supervisor and alert when an intervention – such as stopping work, resting, and allowing the body to cool-down – should happen.

In the absence of such a system, active monitoring such as keen observation, a worker-buddy system that pairs employees with each other to do “check-ins,” and encouraging workers to be acutely aware of their body’s signals of heat injury/illness are all ways to help prevent the negative consequences of heat stress on workers.

When an employee begins to exhibit goosebumps or chills, light-headedness, nausea, and/or feels more weak or fatigued than usual, likely they are experiencing heat exhaustion. Other indicators include fainting, light-headedness, unusually hot skin, excessive sweating, potential vomiting, and difficulty working.

If the worker experiences hallucinations, behavior changes such as aggressiveness, irritability, confusion, and/or irrational tendencies, feels week, or is no longer able to work, their core body temperature may have reached greater than 104°F or 40°C. Likely, this person is experiencing exertional heatstroke. This is a medical emergency and the person needs to be immediately cooled in an ice-water bath.

Flexible work-rest schedules can make a difference

Again, given the person’s biological sex, age, genetics, and diseases, people on your workforce will react differently to working in hot and humid conditions. The main way to “customize” a heat safety program for a diverse team is to be flexible in work-rest schedules. Not all workers will need a break at pre-designated intervals. The body signals outlined above will dictate when rest is needed, where cooling (finding shade and/or air conditioning, and removing excess clothing) and hydration should be emphasized.

During the rest periods, continue to observe individual workers and check their ability to return to work every 10-15 minutes. Because each person will respond completely differently to working in the heat, only that individual can indicate when they’re ready to safely return to work.


Kenny, G.P., Notley, S.R., Flouris, A.D. and Grundstein, A., 2020. Climate Change and Heat Exposure: Impact on Health in Occupational and General Populations. In Exertional Heat Illness (pp. 225-261). Springer, Cham.

Budd, G.M., 2008. Wet-bulb globe temperature (WBGT)—its history and its limitations. Journal of Science and Medicine in Sport, 11(1), pp.20-32.
Regulation, T.R.A.D.O.C., 2016. 350-29. Prevention of heat and cold casualties. Fort Eustis, VA: US Army Training and Doctrine Command, Publication TRADOC Regulation, pp.350-29.

Coco, A., Jacklitsch, B., Williams, J., Kim, J.H., Musolin, K. and Turner, N., 2016. Criteria for a recommended standard: occupational exposure to heat and hot environments. control Ccfd, editor.

Nicole Moyen leads R&D at Kenzen, the smart PPE innovator focused on physiological monitoring and the prevention of heat injury and death among workers. Kenzen’s real-time heat monitoring system is used by companies to keep workers safe from heat. Moyen has a decade of research experience in industry and academia related to human physiology and wearable devices and advises companies on heat stress physiology and dehydration. Nicole has an M.S. in Exercise Physiology and is currently finishing her PhD in Biology from Stanford University.

Heat stress a common cause of fatigue, exhaustion

Heat stress a common cause of fatigue, exhaustion

Workers must be aware of many negative consequences

heat stress worker

Tired stress worker sweat from hot weather in summer working in port goods cargo shipping logistic ground, Black African race people.

Occupational heat stress is the heat load to which someone is exposed in the workplace, which is a function of the environment, physical exertion and clothing.

Heat stress causes increases in both skin and internal body temperatures, leading to dehydration if fluid lost to sweating is not replaced by drinking.

Increases in internal temperature and dehydration have many negative consequences. For instance, the cardiovascular system can become strained, the kidneys are forced to work harder, and cognitive function and decision-making can become impaired.

As a result, occupational heat stress increases the risk of heat illness, elevates the risk of accidents, doubles the risk of injury, and can cause profound decreases in work productivity.

The common denominator underlying these statistics is that heat stress accelerates the development of fatigue, which can ultimately result in exhaustion. This fatigue is caused by a multitude of changes in the body.

By understanding how heat stress promotes the development of fatigue, countermeasures can be put into place to ensure a safe and productive work environment.

Accelerated fatigue

Heat stress accelerates the development of fatigue in two ways — both of which are mostly dependent on how elevated internal temperature becomes.

First, heat stress increases the demand on the cardiovascular system. The goal of the cardiovascular system is to maintain blood pressure so that oxygen-rich blood can be delivered to the active tissues, such as the working muscles and brain.

Heat stress makes this more challenging such that blood pressure is lower during physical work in the heat compared to the same workload when carried out in a cooler environment.

This lower blood pressure during heat stress is accompanied by a higher heart rate to help offset a lower volume of blood ejected from the heart with every beat.

As a result, the demand on the cardiovascular system is greater, which makes physical work in the heat more difficult compared to in cooler conditions.

Importantly, all of this can be made worse by dehydration.

Impaired nervous system

Heat stress can also impair functions of the nervous system.

The nervous system is a way in which signals can be rapidly transmitted throughout the body. For instance, during physical work, nerve signals from the brain tell the muscles to carry out a given task.

Heat stress can alter this process such that to carry out a given task (for example, moving something from one place to another), the nerve signal must be larger during heat stress compared to when the task is carried out in cooler conditions.

As a result, it is more difficult for workers to carry out their normal tasks during heat stress.

Prevention measures

Preventing heat stress-related fatigue and exhaustion involves limiting increases in body temperature and the development of dehydration.

If heat exhaustion (a type of heat illness) is suspected, it is encouraged that the worker be removed from the hot environment and fluids are replenished.

Heat exhaustion is serious, but not life-threatening. However, forcing a worker to continue to work despite being exhausted increases the risk of exertional heat stroke, a life-threatening condition.

This is why it’s important to take steps to minimize increases in core temperature and keep workers hydrated throughout the workday.

When working in a hot environment, it is recommended that workers and their supervisors adhere to recommendations by governing bodies.

Implementing these recommendations will largely prevent sustained increases in body temperature and dehydration.

Such recommendations include provisions for workers taking frequent breaks in cooler environments, giving workers regular access to cool fluids and encouraging them to drink, and having workers participate in heat acclimatization protocols — which can improve the capacity of the body to regulate temperature.

Nicole Moyen is vice-president of research and development at Kenzen, a PPE company in New York. She was assisted with this commentary by Zachary Schlader, an associate kinesiology professor at the School of Public Health – Bloomington at Indiana University, as well as Jessica Freemas, a PhD student studying under Schadler.

This article was featured in OHS Canada, and you can see the original here.

How radiant heat increases injury, illness risk for rooftop solar workers (and four prevention tips)

How radiant heat increases injury, illness risk for rooftop solar workers (and four prevention tips)

by Nicole Moyen

You can see the original article in Solar Builder, here.

Working on a rooftop, closer to the sun and out of the shade, puts workers at increased risk for heat injuries and illnesses. The good news is that heat illnesses are 100 percent preventable if you understand what happens to the body while it’s working on that hot rooftop.

The science

When working in the heat, your heart rate will be higher for the same workload, which makes the work feel harder. Increasing heart rate is the body’s most common response when it is exposed to heat over a period of time during labor. The heart helps the body compensate for several changes that are happening simultaneously to allow the worker to keep pace with his/her activity.

The muscles that are moving the body during work need energy to keep functioning. This energy comes from the types of food workers eat, but oxygen is needed to metabolize that food to make energy for the working muscles. This necessary oxygen is carried in the blood, and delivered to the muscles. The heart is the organ that pumps the blood throughout the body. The harder you’re working, the faster your muscles need that energy, and therefore oxygen. As a result, the heart must pump the blood faster to the working muscles, leading to an increase in heart rate.

Your heart rate typically goes up in parallel to how hard you’re working under temperate weather conditions on a job site. But in the heat, there is added strain to the system, because the blood not only needs to go to the working muscles, but also the skin to get rid of body heat.

When it’s hot outside, your temperature will start to rise. One of the main ways we get rid of body heat (along with sweating) is by increasing the blood flow to our skin. Blood carries the heat away from the core to the skin. The harder a person works in the heat, the faster his/her body temperature increases, and the stronger the need to get rid of that heat to stay safe. So not only does blood need to go to the muscles to keep working, but also needs to go to the skin to get rid of heat. This is why your heart rate will be higher when working in the heat vs. working in a temperate climate.

Dehydration can exacerbate the effects of heat stress because there is less water (or blood volume) to be sent to the working muscles, and skin, and to be lost through sweat. This means your heart has to work even harder to pump the blood needed at the working muscles and the skin, so heart rates will be even higher when working in the heat dehydrated. When dehydrated, your body also tries to conserve water which means that your sweat rate goes down. With a lower sweat rate, you can’t get rid of body heat as quickly, and so your core body temperature will go up even faster when you’re dehydrated working in the heat (than when you’re well hydrated) putting you at increased risk for heat-related problems.

Prevention actions

Heat injuries and illnesses, including fatalities, happen under these hot conditions which are common in the summer months. But as mentioned, heat illnesses are 100 percent preventable if workers and their supervisors understand what happens to workers in the heat, and take the following 4 actions.

1. Account for radiant heat load.

Solar workers are up on rooftops working directly in the sun, which can pose high risk for heat-related injuries and illnesses. Roofs can range in temperature, but can be upwards of 140°F (60°C) on black roof, for example. Part of this increased risk is due to high radiant heat loads (from the sun). Even on a cool day, if it’s sunny outside, managers should measure the radiant heat load to assess the heat strain on their workers. Radiant heat is measured via black globe temperature, and this measurement should be accounted for when prescribing work/rest schedules for your workers on site. The WBGT (wet bulb globe temperature) accounts for radiant heat, and it should always be factored in at sites where workers are directly exposed to the sun.

2. Stay hydrated.

Start your work day hydrated: you can check your urine color, which should be clear to light lemonade color. Drink 8 oz of water in the morning before heading to work. Throughout the workday make sure to replace the fluids you’re losing through sweat to avoid dehydration. On really hot days, try to drink at least 8 oz (half of a commercial-size water bottle) at least every 30 min if not more often. And after work, minimize the amount of alcohol you drink to avoid dehydration the next day at work.

3. Monitor workers’ heart rates and other vital signs.

It is becoming increasingly easier to monitor the heart rates of every individual on the job through smart PPE worn by the worker that relays warnings to both him/her and the supervisor, and prompts a rest period to avoid dangerously high core body temperatures. If your workers’ heart rates are a lot higher than normal for the same workload (e.g. >15-20 bpm higher), it is likely that they are dehydrated, which exacerbates the effects of heat stress and therefore increases the risk of heat injuries and illnesses.

Avoid high core body temperatures that can lead to heat injuries and illnesses. Monitor core body temperatures and take breaks when necessary to cool the body down, ideally in the shade or an air conditioned space, remove extra clothing layers to help you cool, and rehydrate.

4. Acclimatize to the heat.

Heat acclimatization increases blood volume, which helps to lower heart rate. This means that after acclimatization, your heart rate won’t be as high for the same work in heat, so the body is less strained. Acclimatizing means adapting to hot conditions to minimize the risk of heat illness and death. Heat acclimatization can be accomplished by exercising in the heat, taking saunas or hot water baths after a workout, or simply by working in hot conditions on a daily basis. The biggest changes to the body during the acclimatization process happen in the first 4-5 days of these preparations, but full acclimatization can take up to 2 weeks or longer. After acclimatization, sweat rate will be higher, while heart rate and core body temperature at rest will both be lower. These changes improve the body’s ability to get rid of heat, which helps a person work longer and harder in hot environments without lower risk of heat maladies.

Employing these four action items at your worksite will minimize heat-related injuries and illnesses, and help keep your workers safe in these challenging work conditions.

Nicole Moyen is VP of Research and Development at Kenzen and a heat stress blogger, currently finishing her PhD in Biology from Stanford University. Kenzen is a smart PPE innovator focused on physiological monitoring and the prevention of heat injury and death among workers. Kenzen’s real-time heat monitoring system is used by companies to keep workers safe from heat. 

What “industrial athletes” can learn from professional athletes when it comes to working in heat

What “industrial athletes” can learn from professional athletes when it comes to working in heat

by Nicole Moyen

You can see the original article in Canadian Occupation Safety, here.

Industrial workers can learn a lot about how to maximize their performance and productivity at work by watching how athletes train, eat, sleep, and care for their bodies. Elite athletes are constantly trying to find ways to gain a slight edge over their competition by controlling every possible variable that they can. They must perform in various environmental conditions, including heat, which can lead to a suboptimal performance. Many of the ways athletes prepare for competition in the heat to maximize their performance are practices that can be adopted in the workforce to maximize productivity. Below are tips for commercial workers:

Heat Acclimatization:

Most heat-related injuries and illnesses occur during the first 1-2 weeks of working in the heat, so by acclimatizing (i.e., adapting) to the heat, you minimize the risk of heat illness and death. Acclimatization to the heat can occur via exercise in the heat, sauna or hot water bath, or working in the heat. The largest changes to your body (during the acclimatization process) happen in the first 4-5 days, but full acclimatization can take up to 2 weeks or longer.

After you have acclimatized to the heat, your sweat rate will be higher, your heart rate will be lower, and your core temperature at rest will be lower as well. These changes improve your body’s ability to get rid of heat, which helps you work longer and harder in the heat.

Before competitions in the heat, athletes will acclimatize to the heat either by exercising in the heat for 60+ min per day, or by sitting in a hot water bath (or sauna) after a workout for at least 60-90 minutes per day, for 1-2 weeks.

Note that when initially acclimatizing to the heat, you will likely need to reduce your workload and/or wear less protective gear to help facilitate cooling. Each day, you can gradually work longer or harder, and add on more protective clothing. For example, football players acclimatizing to the heat do not wear their full gear until day 6 of acclimatization, and they minimize practice time to 3-5 hours per day with frequent breaks, to allow their bodies ample time to acclimatize. Athletes also slowly increase their exercise intensity (i.e. workload) and/or duration during the first week of heat acclimatization. These same rules can be applied at the jobsite.

Lastly, you will need to maintain your heat acclimatization by exposing yourself to the heat (either via working in the heat or sitting in a hot water bath/sauna) at least once every 5 days. If this is not possible, then doing a hard workout outdoors or wearing extra clothing (to increase your body temperature) while exercising can help to maintain some of these adaptations.


Another important component of staying safe in the heat is staying hydrated before, during, and after your work in the heat. Athletes are very vigilant of their hydration because they know how much it can affect their performance. The easiest way to make sure that you are staying hydrated is to check your urine color in the toilet bowl. If it is a lemonade color or lighter, you are hydrated. Or if you are urinating at least every 2 hours, you are probably doing a good job staying hydrated as well. Hydration is crucial to keeping your body temperature down, which allows you to stay productive and focused on the job.

Dehydration not only increases the strain on your heart, but leads to a higher core body temperature, which can decrease your performance, mood, and cognition.

Some simple ways to improve your hydration are:

Carry a water bottle with you throughout the day, and make sure that you are drinking at least 8 oz. (half of a standard-sized water bottle) every hour, if not more.
Drink fluids with electrolytes (especially sodium), as it will help to absorb the water you drink. Just watch the sugars in your drinks- you do not need them!
Pace yourself when drinking water- do not chug it! Your body can only absorb water at a certain rate- you can’t just “chug” a bunch of water at the end of the workday— you will just urinate it out. The rule of thumb is that your body can only absorb ~8 oz. (half of a water bottle) every 15 minutes, so try to pace your water drinking to that rate.
You can lightly salt your foods- especially in the first few days of working in the heat. This will help you to replenish the salts you are losing in your sweat and help keep you hydrated.

During exercise and work in the heat, your body utilizes more carbohydrates than normal. This means that adding more carbohydrates to your diet can improve your performance in the heat. However, not all carbohydrates are created equal. Make sure that you are eating more complex carbohydrates like whole grains, beans, fruits, and vegetables that are high in carbohydrates and in fiber, and that you are not eating a lot of simple carbohydrates like fruit juices, sodas, and baked goods that are filled with sugars.

Athletes know that the foods they put into their body are essential to their performance: it is their fuel. This means that you have to pay attention to the fuel you are giving your body and make sure that you are giving your body foods that will improve your performance and productivity on the job. Make sure that you are eating healthy, balanced meals that contain minimal sugars and alcohol, as these two items can leave you feeling lethargic, dehydrated, and sluggish.

As an industrial athlete, you are working your body hard every day, just like athletes in sport. Make sure you train, eat, sleep, and hydrate like an elite athlete so that you can perform well at your job and minimize your risk for heat-related injuries and illnesses. Take a note from the athletes and get your body in tip-top shape so that it is ready for the heat!

To learn more about heat stress, follow my blog on the topic at