Scientists determined the limit of human body cooling capabilities

When a person is hot, the body releases sweat. Evaporating from the skin, water takes heat with it, and the body temperature drops. The better the air circulates, the faster evaporation occurs, and the more effectively we cool down.

This mechanism is so effective that it allows a person to withstand air temperatures significantly higher than their own body temperature for a certain period.

However, as Medical Express writes, researchers from Arizona State University have identified a situation where the cooling mechanism begins to fail. The problem is that its effectiveness depends not only on air temperature and humidity but also on how it moves directly near the skin's surface.

What happens near our skin

When the air is hotter than the skin, its thin layer directly near the body cools slightly. It becomes denser and tends to move downwards.

Simultaneously, the opposite process occurs. Sweat evaporates, the air near the skin becomes saturated with water vapor, becomes lighter, and tends to rise upwards.

Thus, two opposing air currents emerge near the human body. We usually don't even notice them. But in intense heat, dry air, and a complete lack of wind, they can almost entirely counteract each other. The natural air movement near the skin sharply weakens. This, in turn, hinders the evaporation of sweat.

Experiments have shown how significant this effect can be. At 41°C and 10% humidity, sweat evaporation can decrease by 56%. As a result, the body accumulates more heat, and skin and body temperatures rise more sharply than traditional human heat balance models predict.

Павялічыць

For the experiments, researchers used ANDI — a special mannequin with sensors capable of simulating sweating. Scientists also created its computer model and conducted about a hundred simulations under various conditions.

The results showed that if the movement of moist air near the skin is not taken into account, overheating of the body can be significantly underestimated.

According to calculations, after two hours in hot, dry air with no wind, a person's body temperature can be approximately one degree Celsius higher than predicted by traditional human heat balance models.

Why this is important

A more accurate understanding of how the body cools is primarily needed to assess the risk of overheating. Such calculations form the basis for recommendations for people working in intense heat, as well as for the development of cooling systems for rescuers, military personnel, and athletes.

The discovery may be particularly important for enclosed and partially enclosed spaces where there is almost no air movement: tents, production sites, unfinished buildings. As the study showed, dry air alone does not guarantee that sweat will effectively cool a person.

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