Thermal climate and comfort

Termiskt klimat, det vill säga lufttemperatur och relativ luftfuktighet, har stor betydelse för människans välmående. Hur det termiska klimatet upplevs beror på lufttemperatur, strålningstemperatur och luftfuktighet. Det påverkas också av vilken typ av arbete som utförs, om det är stillasittande eller rörligt, samt hur väl anpassad klädseln är för det arbete som ska göras.

The importance of a comfortable thermal environment

Cold, heat and draughts can have direct and indirect effects on health. A temperature between 20-24 °C and a relative humidity between 30-70 % is perceived as a good environment by most people. What is perceived as a comfortable temperature is also affected by the speed of the air, i.e. the draught.

Too high or too low a temperature can be uncomfortable and affect both physical and mental performance. Direct effects in hot climates include headaches and fatigue. Cold climates can cause problems with joints and lung disease. Cardiovascular disease is common in both hot and cold climates. Indirect effects include difficulty concentrating, which can contribute to an increased risk of accidents. When the body is exposed to thermal stress, the absorption of airborne pollutants also increases because we have to breathe more.

Indoor relative humidity is linked to temperature. Heating up cold outside air reduces the relative humidity (RH). RH is a measure of how much water vapour the air can hold at a given temperature. At RH levels above 70 %, the risk of mould and mite growth increases. Dry air causes the mucous membranes in the eyes, nose and throat to dry out. This can lead to irritated and dry eyes, dry skin and lips, and nosebleeds. Static electricity can occur when the relative humidity is below 40%. As well as being unpleasant for the person exposed to the discharge caused by the static electricity, it can cause interference in electronic systems.

OEL values and guidelines

There are no exact temperature limits for how hot it may be at work, either indoors or outdoors. The Swedish Work Environment Authority's regulations on the design of workplaces state that indoor workplaces must have a suitable thermal climate adapted to the activities carried out. The temperature and air velocity must be adapted to the type of work, whether it is light or heavy, mobile or sedentary.

The general advice from the Swedish Work Environment Authority is that the air temperature for light and sedentary work should be within the range of 20-24 °C in winter and 20-26°C in summer. Otherwise, a more detailed investigation and risk assessment must be carried out. For sedentary work, the air velocity should be less than 0.15 m/s. For more mobile work, or at higher air temperatures, the air velocity may be higher. If different tasks are performed in different parts of a room, they may require different thermal climates.

Permanent outdoor workplaces should be designed to protect workers from the weather. Temporary outdoor workplaces should, as far as possible, be designed to protect workers from the weather. The Public Health Agency of Sweden has issued general advice on indoor temperatures that apply to living spaces and general indoor environments (FoHMFS 2014:17). Recommendations for ventilation, air quality and thermal climate can also be found in international standards.