What Indoor Temperature Is Too Hot for Humans and Why

Indoor temperatures above 75°F (24°C) can cause discomfort and even health issues.

Prolonged exposure to temperatures above 80°F (27°C) can lead to heat-related illnesses.

The World Health Organization recommends keeping indoor temperatures below 77°F (25°C) to prevent heat stress.

At 82°F (28°C), the human body starts to lose water more quickly, leading to dehydration.

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A reasonable working temperature is not just a matter of personal preference, but a crucial aspect of ensuring worker safety and comfort. Employers must assess the risk of extreme temperatures in their workplace.

The Workplace (Health, Safety and Welfare) Regulations require employers to provide a reasonable indoor temperature, which depends on the work activity and environmental conditions. You can't just set the thermostat and forget about it.

To determine a reasonable temperature, you must consider the specific needs of your workers and the tasks they perform. For example, workers in construction sites have different temperature requirements than those in office buildings.

Employers must act on any findings by putting controls in place, including temporary or seasonal ones. This might involve providing fans or air conditioning during hot summer months or heating in cold winter months.

If you're unsure about what constitutes a reasonable working temperature, use our heat stress checklist if workers are at risk from extreme temperatures. This will help you identify potential risks and take steps to mitigate them.

Here's a quick reference guide to help you determine a reasonable working temperature:

High temperatures can have a significant impact on our health, and it's essential to understand the risks involved. Exposure to high temperatures can cause our metabolic rate to increase, which can lead to heat exhaustion and heat stroke.

In one study, participants' metabolic rate increased by 35% when exposed to 40℃ (104F) and 25% RAH, and by 48% at 40℃ (104F) and 50% RAH. This is a significant increase, and it's essential to take precautions to avoid heat-related illnesses.

Prolonged exposure to high temperatures can also cause our core temperature to rise. In the 50℃ (122F) and 50% RAH condition, participants experienced a rise in core temperature of 1℃, or 1.8 Fahrenheit.

Heat can also affect our heart rate and breathing rate. In the 50℃-50% RAH condition, participants sweated 74% more and experienced a 64% increase in heart rate compared to baseline.

Here are some key health impacts of high temperatures to be aware of:

It's essential to take precautions to avoid heat-related illnesses, especially for older adults, who can't sweat as effectively.

Human bodies can only tolerate heat for so long before they start to suffer.

The human body's ability to cool itself is crucial in hot temperatures.

Prolonged exposure to temperatures above 38°C (100.4°F) can cause heat-related illnesses, including heat exhaustion and heatstroke.

Even mild temperatures above 25°C (77°F) can cause discomfort and decreased productivity.

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The human body has a strict temperature limit, and it's not just about reaching a certain number. The core temperature of 43 degrees C (about 109.4 degrees F) is the upper limit of survival.

This temperature is the point at which the body's systems start to shut down, and it's a number that's not to be taken lightly. Anyone who reaches that core temperature would die, with a mortality rate of 99.9%.

Heat can be a silent killer, worsening pre-existing issues like cardiovascular or renal disease.

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Humans can't endure high temperatures for an extended period. The human body can't tolerate its temperature reaching 43 degrees C (about 109.4 degrees F).

At temperatures above 40 degrees C, the body's ability to dissipate heat becomes impaired. In a study, participants exposed to 50℃ (122F) and 50% RAH experienced a 56% higher metabolic rate than baseline, and their core temperature rose by 1℃ (1.8F).

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This increase in metabolic rate is not accompanied by an increase in core temperature at lower temperatures. For instance, at 40℃ (104F) and 25% RAH, the metabolic rate increased by 35%, but the core temperature remained the same.

The body's response to high temperatures is complex and influenced by factors like humidity. In the study, participants in the 50℃-50% RAH condition sweated 74% more and experienced a 64% increase in heart rate compared to baseline.

Here's a breakdown of the body's response to different temperature and humidity conditions:

The body's inability to tolerate high temperatures can have severe consequences, including worsening pre-existing conditions like cardiovascular or renal disease.

Temperature and humidity can be a deadly combination. If the air is too humid, your sweat can't evaporate, and you're more likely to experience heat stroke and death.

Scientists use a measure called the wet-bulb temperature to gauge the heat and humidity together. This is the temperature if a thermometer was covered with a wet cloth to evaporate heat, approximating the cooling of skin by sweat.

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The wet-bulb temperature must be a few degrees cooler than the inside of your body for heat to flow away from your body. Otherwise, metabolic heat builds up inside your body, leading to a high fever and heat stroke.

Here are some key temperature and humidity conditions to avoid:

In these conditions, the researchers found that participants' metabolic rate increased significantly, with the highest increase at 50℃ (122F) and 50% RAH.

Temperature and humidity can have a significant impact on our bodies, especially when it comes to heat stress.

Exposure to high temperatures and humidity can cause our metabolic rate to increase, which means we burn more calories to cool down. In one study, participants' metabolic rate increased by 35% at 40℃ (104F) and 25% relative air humidity (RAH), and by 48% at 40℃ (104F) and 50% RAH.

High humidity can also make it harder for our bodies to cool down, as it prevents sweat from evaporating efficiently. In the 50℃-50% RAH condition, participants sweated 74% more and experienced a 64% increase in heart rate compared to baseline.

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As we try to cool down, our breathing rate increases to help dissipate heat. In the 50℃-50% RAH condition, participants' breathing rate increased by 23%, and the amount of air they could inhale and exhale per minute increased by 78%.

Some people may be more susceptible to heat stress, especially those with pre-existing medical conditions. If you're planning to spend time outdoors in hot and humid weather, make sure to stay hydrated and take regular breaks to cool down.

Here's a summary of the effects of temperature and humidity on the human body:

Humidity can be the difference between a tolerable temperature and a potentially life-threatening situation. If it's too humid, your sweat doesn't evaporate, and your body can't cool itself effectively.

The wet-bulb temperature is a measure of both heat and humidity, and it's a crucial indicator of how well your body can cool itself. If the wet-bulb temperature is a few degrees cooler than the inside of your body, heat will flow away from your body, but if it's not, you're at risk of heat stroke and death.

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Exposure to high temperatures and humidity can have serious consequences for your body. In a study where participants were exposed to different temperature and humidity conditions, researchers found that metabolic rate increased by 35% at 40℃ (104F) and 25% relative air humidity (RAH), and by 48% at 40℃ (104F) and 50% RAH.

Here's a breakdown of the conditions and their effects on the body:

The study also found that participants in the 50℃-50% RAH condition sweated 74% more and experienced a 64% increase in heart rate compared to baseline.

As we've discussed, a temperature of 90°F (32°C) or higher can be considered too hot for humans, especially for vulnerable populations like the elderly and young children. This is because their bodies have a harder time regulating their temperature in hot environments.

Prolonged exposure to temperatures above 90°F can lead to heat-related illnesses, such as heat exhaustion and heat stroke. These conditions can be life-threatening if not treated promptly.

In fact, the American Red Cross recommends taking regular breaks in cool or shaded areas to avoid heat exhaustion and heat stroke. This is especially important when engaging in strenuous activities outdoors.

A temperature of 95°F (35°C) or higher can be particularly hazardous, as it can cause the body to lose heat at a rate that exceeds its ability to cool itself. This can lead to a range of symptoms, including headaches, nausea, and dizziness.

In extreme cases, temperatures above 100°F (38°C) can cause the body's internal temperature to rise to dangerous levels, potentially leading to brain damage or even death. This is why it's essential to take precautions when working or spending time outdoors in extremely hot weather.

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