Our concern was to measure the air quality in classrooms, to analyse its consequences, and to find out about possible limitations in the students' performance, such as concentration problems. For this purpose, we recorded all changes in the air of the classroom with the air analyser air-Q between 7 am and 1:30 pm. The special focus of this measurement was on substances such as carbon dioxide(CO₂), oxygen(O₂) and volatile organic compounds(VOC gases). But the temperature and possible noise were also examined more closely.
Ventilate properly to increase motivation to learn
The CO₂ concentration in the air showed a similar pattern on both days, which can be explained by the same distribution of lessons and breaks. The first increase in CO₂ levels in the morning can be explained by the occupation of the classroom and the start of the first lesson. A big difference on both days appeared at 8:30 am, at the time of the first break. On 18 June, the windows were opened afterwards and the classroom was properly ventilated. This allowed fresh air to flow into the room and the carbon dioxide decreased. On 19 June, again the windows remained closed. The children's breathing caused the CO₂ content of the air to rise rapidly.
Since the noise from outside would have a disruptive effect on the lessons, the windows were closed again. This led to a dramatic increase in carbon dioxide levels. According to studies, performance deficits can already occur at a CO₂ concentration of 1000 ppm (parts per million). However, over 2000 ppm were measured in the classroom. On the first day of measurement, the value of 3000 ppm was even exceeded at around 10 am.
Thus, a noticeable impairment of the pupils' concentration could be assumed. This impairment manifested itself not only in their lack of concentration, but also in an increased tiredness of the children. Motivation to learn may decrease or even be lost altogether as a result. In addition, spelling or arithmetic errors may increase.
It was not until the ventilation during the long break that the classroom could be supplied with sufficient fresh air again. On both days, the windows remained open after the break.
The development of the oxygen content in the classroom was opposite to that of the carbon dioxide, as the inhaled O₂ is exhaled again as CO₂. Ventilation was able to replenish the oxygen supply in the room.
At least the classroom is large enough that even over a longer period of time without ventilation, asphyxiation of the students could be ruled out. An oxygen concentration between 18 % and 21 % is generally considered harmless. Corresponding to the highest CO₂ concentration, the lowest O2 value was measured on 18 June at around 10 am. At that time, the oxygen level in the classroom dropped to almost 20 %.
VOC gases are released via the students' breathing and skin. If the room is not ventilated, the concentration of volatile organic compounds increases - similar to carbon dioxide. Here, too, the curves rose considerably on both measurement days around 10 am. However, with approx. 430 ppb (parts per billion), the highest spike was observed on 19 June shortly before 8:30 am. Presumably, this is related to the fact that on that day there was no airing after the first lesson. The release of these gases also contributes to a reduction in the ability to concentrate. However, in this case, an exact evaluation is not clearly possible because the VOC gases are of very different types and accordingly have different effects.
If the VOC concentration in the room increases even when the window is closed and in the absence of people, this is a strong indication of chemical contamination of e.g. laminate floors, wall paints, textiles or mould. To investigate this, the air-Q continued to record various VOC values even after the end of lessons. No increase in these could be detected.
On both measurement days, the room temperature was very high, at times exceeding 27°C. A circumstance that further contributed to a reduction in the students' ability to concentrate. Opening the windows caused a cooling of only 1°C. Relief for the children on such hot summer days could only be achieved by setting up a quiet and mild fan.
The measured noise level of the classroom did not record any particularly high values during the measurement period. The sound pressure level curves very clearly reflected the alternation of lessons and breaks, as quiet and loud phases occurred at the same times and in the same rhythm on both days. Since no outside noise penetrates during lesson times, the maximum values of up to 70 dB(A) (decibels) determined on both days are still below the limit of 80 dB(A), which is harmful to health.
Furthermore, the humidity in the classroom was measured. Here, too, the highest concentration of over 43% was determined at around 10 am on both days. A humidity of 40 to 60% is recommended for well-being and thus performance. While these guideline values were largely adhered to on 19 June, the humidity content of the air dropped permanently to values below 40% from around 10:15 am on the first day of measurements. Dry air can not only dry out the respiratory tract and promote the spread of pathogens. It is also perceived as unpleasant and can thus impair performance.
Our conclusion: Avoiding concentration problems and increasing motivation to learn by analysing air quality
Like the classroom studied, most German school buildings do not have a built-in ventilation system. Thus, it can be considered representative of many German classrooms. Particularly striking in our measurements were the rapid increases in carbon dioxide and VOC gases when the windows were closed. Provided that no disturbing noise enters the room from outside, it is possible to ventilate for a long time during the warm season. In the cold seasons, however, this is rarely an option. It can be assumed that at these times the levels of both CO₂ and volatile organic substances in the air reach a much higher level. This has a considerable impact on the students' ability to concentrate and thus on their learning ability.
Therefore, we recommend that teachers regularly open the windows and properly ventilate the room. However, even with proper ventilation between lessons - as in this case - the carbon dioxide and VOC content can reach performance-limiting levels. General losses in the children's learning ability due to poor air cannot be ruled out.
However, for a more accurate assessment of the air quality of the classroom, continuous measurement over a longer period of time would be required.
(Cover picture: Freepik)
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