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Physical and chemical environmental factors

The ASTF can perform a whole series of measurements for its members, designed to assess the quality of the working environment. These measurements concern both physical and chemical parameters.

1 - Physical ParamEtres

Wellbeing of the workplace is dependent on many factors, one of which is thermal comfort. A number of parameters enable the following to be evaluated:

  • the ambient temperature;
  • relative humidity;
  • air speed;
  • thermal radiation.

These four parameters are interpreted in the light of the physical effort needed by the work to be performed and the clothing which is worn.
To be in a state of thermal comfort, a person must wear a reasonable quantity of clothing without being too warm or too cold. Thermal comfort is important both for the wellbeing of the individual and to ensure his or her productivity. It can be achieved only when the temperature, humidity and air movement fall within the limits of what is referred as the “comfort zone”.
In offices it is important to maintain stable temperature conditions. A departure from the comfort zone, however small, can cause stress and affect productivity and safety. Stressed workers are less tolerant to uncomfortable conditions.

Ambient temperature (°C)

This must be stable during the working day.
The Labour and Mines Inspectorate (ITM) recommends maximum and minimum values (ITM-SST 1814.1):

  • The minimum temperature is 20°C for offices. The minimum temperature must be reached before work begins each day.
  • The maximum temperature at the workplace must not normally exceed 26° in the case of air conditioned premises.

The difference between the outside temperature and the inside temperature of air conditioned premises working with a cooling system must not exceed 8°C unless technological imperatives dictate otherwise.
Some recommendations applicable to air conditioned premises suggest an ambient temperature between 20° and 24°C in winter and 22° and 26°C in summer.

Relative humidity (%)

ITM (ITM-SST 1814.1) recommends that, in the case of premises with artificial ventilation, the relative atmospheric humidity in working premises must not fall below 30% under normal conditions.
Moreover, the relative humidity must not exceed certain values dependent on the ambient temperature:

Temperature °C

Relative Humidity %









In offices in Luxembourg we practically never encounter air which is too humid, but we do often experience the problem of air which is too dry. The rate of relative humidity depends greatly on the outside level. Outside air is much drier in winter than in summer and when outside air is heated, an additional humidity loss occurs.

When the ambient air is too dry, sensitive individuals may experience problems, such as irritation of the mucous membranes and of the skin (irritation of the eyes, problems caused by wearing contact lenses, dry throat, dry nose, itching skin etc.) accompanied by a greater susceptibility to possible illnesses, mainly affecting the nose, throat, ears and lungs.

Air speed (m/sec)

Measurement of the air speed for sedentary office work should show a figure of less than 0.15 m/s. Air speeds in excess of this value are perceived as draughts and must therefore be avoided.
A substantial air speed will result in a loss of body temperature through the convection mechanism. The person concerned will feel cold even if the ambient air temperature is correct.

Thermal radiation 

A substantial difference in temperature between the surfaces around an individual or direct radiation of sunlight, tend to facilitate asymmetrical exchanges by radiation with certain parts of the body. For example, a cold window or a warm ceiling may produce a cooling or warming effect of just part of the body; this can cause discomfort.
The radiation temperature can be evaluated indirectly by using a thermometer with a black bulb.


For office work, three main factors come into play:

The rate of carbon dioxide (ppm)

This measurement enables us to determine whether the renewal of air is sufficient at the workplace.
In an office, the main sources of C02 release are air breathed out by employees and also cigarette smoke (normally no longer encountered at the workplace) and exhaust gases (for example, if windows are open and look out onto a busy main road).
High concentrations of C02 cause headaches, fatigue and difficulty in concentrating.
Air renewal is considered satisfactory if the measured rate of C02 does not exceed 800 to 1000 ppm.

Formaldehyde level (ppm)

Formaldehyde is a gaseous substance with a bitter odour at ambient temperature which irritates the eyes and respiratory tract. It can also cause allergenic reactions.
Because of its many uses, formaldehyde may be present in offices or residential premises. The sources of formaldehyde may be in the furniture, wall coverings, woodwork, particulate panels, plywood, disinfectants and cleaning products, cosmetics and tobacco smoke. Formaldehyde may even be emitted by clothing.
In indoor areas, the concentration of formaldehyde should not exceed 0.1 ppm (0.1 part per million).
The main symptoms caused by an excessive concentration of formaldehyde are irritation of the mucous membrane and respiratory tract and allergenic manifestations.

Presence of volatile organic compounds (VOC)

In general VOC concentrations are low in offices, but the concentration may be higher after conversion or refurbishment work.
The sources of VOC vary widely.
Their presence can be assessed qualitatively and quantitatively by chemical absorption analyses over a 14 day period.
The toxic effects of VOCs are variable, depending on the compounds which are encountered and their concentration. Irritations of the skin, mucous membranes, bronchial tract and brain are possible.

Summary table:


Empfohlene werte


20-26 °C

Relative luftfeuchtigkeit



<0.15 m/sec


<800-1000 ppm

For further information or to obtain measurements, please do not hesitate to contact us.