Forskningscenter for Arbejdsmiljø (The National Research Centre for the Working Environment): Dry indoor air cause of objectionable indoor climate among office workers

Published: January 2019

Physical discomfort reported among office workers, such as dry eyes, headaches and tiredness, is most often linked with poor or no ventilation. But two articles published by the National Research Centre for the Working Environment (NFA) show that air humidity also plays a crucial role.

A new analysis of the current knowledge that is summed up in two new reviews, shows that it will take more than the daily ventilation of office spaces to improve their indoor climate. “The level of humidity in the air plays a highly crucial role in indoor climate and employees’ wellbeing, and unfortunately this is overlooked today,” says the author.

“For more than 40 years, engineers have recommended ventilation and the regulation of temperature as the means to control the indoor climate. This has meant that the impact of relative humidity has been significantly underestimated,” says Peder Wolkoff, author of the new reviews, former indoor climate professor and currently Senior Researcher at the National Research Centre for the Working Environment.

The current recommendations on ventilation come from studies carried out on young students in the 1970s and air humidity did not play a role in the young adults’ wellbeing. But in modern office environments where people are aged 35–70 years old, conditions are very different.

“The results show that the recommendations can beneficially be supplemented with more nuanced assessments, which also include for example, physiology and airway toxicology,” says Peder Wolkoff.

Relative air humidity must be at 40–50%

Peder Wolkoff’s work shows that people who work in offices with a relative air humidity of 40–50% generally feel that the air is not so dry and that the offices are more comfortable to work in.

In office environments where the relative air humidity is less than 30%, greater numbers of employees complain about irritation of the mucous membranes in the eyes, nose and pharynx. These employees generally suffer headaches more and are more tired. However, if the problem is due to a lack of air humidity, ventilating the room is not a viable solution.

“Ventilating the room is not appropriate if air humidity plays a role. During the winter months, relative air humidity in office environments can easily fall below 30% because the ventilation replaces the indoor air with dry outdoor air,” says Peder Wolkoff. However, he points out that with higher air humidity, there results are more positive.

The study shows that with a relative air humidity of 40–50%, the risk of being infected by an influenza virus and of dust particles swirling up from floors is diminished. This means that in terms of wellbeing and health among staff, there are improvements to be gained by focusing more on humidity.  Nevertheless, people still have a long way to go in this regard.

Almost no one is working on air humidity today

Peder Wolkoff is convinced that it is not just office workers who would benefit if greater focus on air humidity was on the agenda.

“Air humidity is generally low in educational institutions and office environments, and this has a number of negative effects. A focused effort in this area can really benefit the affected people. But there is still a need for research that can explain how air humidity influences comfort and health in indoor climate,” emphasises Peder Wolkoff.

Symptoms with low air humidity

Typical symptoms are:

- Dry/itchy eyes

- Tiredness

- Headache

-  Affected mucous membranes in nose, pharynx and throat.

The symptoms are caused by low air humidity in combination with:

-  Other effects in the indoor climate

-  Personal risk factors

-  Outdoor air humidity, especially during the winter season


With relative air humidity of 40–50 % in office environments, employees gain:

- Noticeably improved air quality and comfort

- Fewer symptoms such as dry eyes, tiredness, headaches and affected mucous membranes

- Improved work-related performance

- Fewer sickness absences, e.g. with lower risk of being infected by influenza viruses

-  Positive effect on the voice – for some people

Jeanet Berg: The office environment benefits from humidification

“The indoor climate of offices has a major impact on employees’ wellbeing, efficiency and health – and air humidity plays a crucial role. Countless numbers of studies carried out around the world have shown this, and now the National Research Centre for the Working Environment has shown it again with these two studies. It is a victory for all office workers that there will now be greater focus on dry air at offices and what can be done about it. Installing a humidifier in an office is simple to do and will help make the unwelcome effects of dry air a thing of the past.”


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