N°4 – Notion of comfort in terms of temperature and humidity training (VTC level)

The temperature of our skin is between 30 à 35 [°C] (86 to 95 °F) depending on the season. It is natural for us to find it pleasant to be in an ambient temperature which is reasonably lower than this skin temperature.
But:

• If the air is too dry our perspiration evaporates very easily, and our skin can become too dry. While this situation exists in the Sahara desert, it can also be the case for winter sports. In fact, with the air being cold, our body heat is easily evacuated by convection and radiation, and our “sweat” production will be minimal. Our skin can therefore lack humidity (cracking or chapping).
• If the air is too humid our sweat evaporates with difficulty, and having damp or sweaty skin is not very pleasant. The hotter the air, the more sweat the body has to produce to evacuate its heat. However if the air is humid, it is difficult for this sweat to be evacuated, and we will rapidly be “drenched”.

 
We can therefore summarise the 4 main situations:

• The temperature is slightly chilly and humidity is reasonable:

To limit our heat losses we are able to insulate ourselves by wearing certain garments. Light healthy and invisible perspiration will adjust the evacuation of energy. It is a perfectly tolerable normal situation. 

• The temperature is a bit chilly and humidity very low (dry air):

Heat is evacuated very easily (cold air), and our body produces very little perspiration. This evaporates very quickly (dry air), and our skin risks becoming too dry.

In addition this situation increases the phenomenon of static electricity inside the buildings. In the winter we can experience small unpleasant “shocks” in the corridors of hotels or offices, when the air is too dry.

• The temperature is warm and humidity reasonable:

We wear the minimum amount of clothing that is morally acceptable, and a little more evaporating perspiration adjusts the energy evacuation. It is a very tolerable and normal situation.

• Temperature is warm and humidity high:

Heat is difficult to evacuate (hot air), our body produces sweat. This is not easily evaporated (humid air), and we risk becoming soaked. If we can’t lower the temperature or remove clothing, air movement has to be increased to help our sweat evaporate by installing a fan in our office.
In addition this situation is not good for conserving papers or pictures and will cause problems in photocopying rooms or museums.

We should nevertheless put the problem into perspective. Simple temperature control will in most cases be sufficient. In our french temperate climate without any humidity control, the majority of buildings offer acceptable comfort conditions both in winter and in summer.

For certain specific premises, such as museums, laboratories, swimming pools, controlling humidity will obviously be essential.