Temperature humidity

A large number of other aspects determine whether people feel comfortable in a room or not. The primary aspects are:

A. Individual-related aspects

· the nature of the work;

· clothing;

· general health;

· being easily influenced or not.

B. Environmental aspects

· air temperature and humidity;

· any air currents (draught);

· any heat radiated by lamps and other heat sources;

· air quality (inflow of fresh air and existence of air pollutants in the room).

People working in office environments often complain about the air quality. Complaints include the air being stale, musty or too dry. On this page, we will discuss the causes of a number of common complaints, as well as the means to do something about them.

1. Dry air (humidity)

Air contains moisture to some extent. The absolute amount of moisture the air may hold (the 'humidity') mainly depends on the temperature. The higher the temperature, the larger the absolute amount of moisture the air may hold as water vapour.

Low humidity in practice only occurs in winter. It is caused by cold air being brought in from the outside and heated up. As cold air cannot contain high amounts of moisture, the absolute humidity of the air is low. As the air heats up, it becomes able to hold a much larger amount of moisture. So, if the absolute humidity remains the same, the relative humidity will decrease. For relative humidity is the ratio of the absolute amount of water vapour in the air and the maximum amount of water vapour this air may hold at any given temperature at that time.

The Working Conditions Information Sheet 24, Interior Environment (SDU, 2013) states that no connections exists between complaints of air being too dry and relative humidity for the usual humidity values in winter. Only when the humidity is extremely low, as is the case in airplanes, is there a possibility that low humidity may cause irritation to the bronchi and a sensation of the air being too dry. Humidity is considered to be extremely low when it is less than 15%. This percentage is hardly ever to never reached in Dutch offices, as the Dutch winter is not terribly cold and the building itself and the people working in it constantly emit (a lot) of moisture.

People are generally unable to accurately estimate relative humidity. The complaints related to low humidity are generally not caused by the low humidity itself, but by irritants in the air, like dust and pollutants (e.g. as emitted by equipment and printers). In particular when the temperature is high and little fresh air flows in, they may cause complaints and irritation to the mucosa.

When temperatures are higher, the dust present in the room (in chair coverings, on desks and in closets, etc.) is easily released up into the air, leading to eye and throat irritation.

2. Stale air

Research by Fang and Fanger, 1997, indicated that air of a high temperature and humidity has a high energy density and, consequently, is experienced as being much more stale and stuffy than air of a low temperature and humidity.

For example: If clean outside air with a temperature of 18 °C and a relative humidity of 30% is heated up to a temperature of 28 °C and has its relative humidity raised to 70%, the percentage of people not satisfied with the air quality will rise from 8 to 60, while nothing has changed about the composition of the air!

In addition, higher temperatures and humidity cause increased emission by fittings and furnishings. This may in turn cause irritation to the mucosa.

3. Actions too take when the air is too dry

As has become apparent, the climate here in the Netherlands generally does not require humidification of inside air. When the air is experienced as being too dry, the solution generally is not to be found in humidifying the air, as most of the complaints are caused by insufficient air quality. What's more, humidification can itself cause further complaints. Improper maintenance of air humidification systems will result in microbiological organisms developing in the water, which may lead to various health problems. Such pollution by microbes is least likely to appear when humidification systems are based on steam.

Humidification may only be required for some particular work, like in labs or printing offices, for work-related reasons.

Humidity-related complaints can be prevented by ensuring a proper inflow of fresh air, limiting the accumulation of dust and maintaining relatively low temperatures (< 21 ºC).

Approach in regular situations:

Measures that may help reduce humidity-related complaints:

·

Ventilation

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The ventilation system is to be in proper working order, so plenty of fresh air enters the room. When in doubt about the state of the ventilation system, report this at the building's service desk.

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If possible and permitted, ventilate the room as well as possible by opening windows. To prevent any consequential complaints of draught, open the windows during breaks.

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Preventing or reducing dust accumulation:

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Install sources of pollutants like photocopiers and printers outside the workspace.

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Make sure that floors, desks, windowsills and other horizontal surfaces can be easily reached for cleaning. This means:

ü

adopt a clean desk policy

ü

bind cables together and place computer cases underneath the desk.

ü

put books, folders and binders in closed closets.

ü

do not place anything on top of closets.

ü

do not put boxes on the floor.

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Regularly remove the dust from plants and throw away withered plants/flowers.

·

Temperature:

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Lower temperatures to 20-21 degrees.

·

Other:

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Do not attach water bowls to radiators. Only a very small amount of water evaporates into the air. At the same time, these bowls are the perfect breeding ground for mould and bacteria, which will actually worsen the complaints.

Approach in extreme situations (winter):

At times of low outside temperatures (long-term frost with daytime temperatures below freezing), inside air humidity may become extremely low (< 15%). This hardly ever occurs, but if it does, this low humidity may contribute to the air being experienced as being too dry. People wearing contact lenses are especially affected. People with asthma or other complaints of the airways or skin can be very sensitive to low humidity as well. In addition to the measures detailed above, the company doctor may advise that further measures need be taken. The company doctor may, for instance, advise the Facility Department to install a temporary mobile air humidifier.

Sources:

- Working Conditions Information Sheet 24, Interior Environment, instructions for healthy and comfortable buildings. 3rd edition, 2013.

- Fang, L., Wyon, D.P., Fanger P.O. (2003) Sick building syndrome symptoms caused by low humidity. In: Proceedings of Healthy Buildings 2003, Vol. 3, pp. 1-6.