What means air quality?
Air quality is a measure of the quality of air in interior spaces
The objective measure of the air quality is carbon dioxide (CO2). This colorless and odorless gas is exhaled by human beings, depending of the age and the physically activity.
In the open air the carbon dioxide concentration fluctuates between 360 ppm (parts per million) in clean air areas and 700 ppm in cities. The recommended maximum value for interiors is 1,000 ppm CO2, the limit for offices 1500 ppm.
In a classroom, the CO2 concentration increases strongly during a lesson, depending on the number of students and the size of the room. Thus, values of 3,500 ppm after a lesson are not uncommon!
In a freshly ventilated office space with 25 m² of floor space, the carbon dioxide concentration increases after closing the insulating windows within an hour to 2,000 ppm when there four adults are active.
Why is air quality so important?
Air quality affects the well-being of those present.
Carbon dioxide may be only toxic at for Humans at a concentration of 5 vol .-% (i.e., 50,000 ppm), but causes at much lower concentrations (i.e., from values from 800 to 2000 ppm) nonspecific mood disorders such as headache, fatigue, lack of concentration and performance degradation. Not only teaching tired students, but also the bad air in the classroom!
Parallel to the carbon dioxide content, the concentration of a variety of other substances increases in the ambient air. On the one hand, these are by the human produced smell and chemical messengers, on the other exhalations of the room and the furnishings may be added, such as formaldehyde, polychlorinated biphenyls (PCBs), detergents and solvents.
These substances can cause harm to the health (sick building syndrome), but their concentration is compared to that of CO2 difficult to determine.
How can the air quality in the room be improved?
Only by sufficient airing!
However, this is problematic in practice because:
- Every person perceives the air quality in the room subjectively different. Those who just entered a crowded room, assess the air quality is usually much worse than those who remain there for some time. (Habituation effect!)
- In winter, the saving of heating costs is in the foreground, the more at the currently prevailing fuel oil and gas prices. The fact that "thick" air reduces the performance of those present becomes less important.
- Through energy-saving improvements to buildings, the "natural" ventilation through cracks and joints has continuously decreased over the past thirty years. Most people are not aware of the fact that today they have to ventilate more for a constant interior climate than before.
How to ventilate sufficient?
By opening and closing the windows depending on the carbon dioxide content of the room air. This results in consistently good room climate in offices and classrooms, and energy is not wasted unnecessarily.
As human beings cannot perceive carbon dioxide with his senses, he has to use a measuring instrument for this purpose, preferably our air quality indicator light.
Tiresome discussions about "window open or prefer closed" soon become a thing of the past with the air quality traffic light and in the room there is in the truest sense of the word a good climate!