Many people gather in a classroom: and breathe. An estimated eight litres of air per minute flow through each nose. This contains CO₂, carbon dioxide, which causes fatigue, headaches and concentration problems. This, of course, inhibits the pupils' ability to absorb information. Finally, a good indoor climate with a sufficient supply of fresh air is essential for concentration and performance.
In order to be able to memorise learning content in the long term and to achieve full examination performance, students must be provided with the appropriate framework conditions. The quality of the air in the classroom is also of great importance. Proper and sufficient ventilation supports the required ability to concentrate in a simple way: Sufficient fresh air supply minimises the amount of carbon dioxide in the room and provides more oxygen. Regular ventilation also reduces airborne pathogens, such as aerosols. Furthermore, moisture is removed to the outside and the air humidity is lowered, which reduces the risk of mould. In addition, odours and VOCs emitted from furnishings are removed.
CO₂ traffic lights indicate too high CO₂ concentrations as a ventilation indicator
Even in small quantities, CO₂ leads to performance deficits. This is because the brain needs sufficient oxygen to be able to work at full capacity. However, you usually only notice an increased CO₂ load when it is already too late. This can happen quickly, especially in crowded rooms. The Federal Environment Agency therefore recommends that the CO₂ concentration in classrooms should not exceed 1,000 ppm, i.e. CO₂ parts per million. Since this is rather abstract, here is a tangible comparative figure: anyone enjoying the fresh air outside is exposed to the minimum CO₂ concentration of 400 ppm.
CO₂ traffic light as protection against diseases
Airing out not only improves mental performance, but also prevents colds caused by viruses, such as Covid 19 viruses. Aerosols are responsible for the spread of the corona virus: tiny particles that get into the room air when exhaled and can spread in suspension over several metres. If there is a high concentration of aerosols in the air in the classroom, the risk of infection increases for everyone. With the help of an air measuring device, you can determine the quality and pollution of the air in the room. If the amount of exhaled CO₂ increases, it can be assumed that the amount of aerosols in the room air also increases. Therefore, the measurements can be used as a tool for corona prevention.
Even though the number of aerosols as well as viruses in the air cannot be measured directly, the carbon dioxide content of the air is a good indicator of when it is time to ventilate. This can reduce the risk of indoor infection. A good ventilation routine is therefore necessary in classrooms. The Federal Environment Agency advises: Ventilate extensively three times an hour, i.e. every 20 minutes, with the windows wide open. This is all the more effective when there is a large temperature difference between inside and outside. When outside temperatures are cold in winter, just a few minutes are enough, while on warmer days the windows must remain open longer to achieve the same effect.
Ideal air values for schools & classrooms
CO₂ levels below 500 ppm are ideal. In full classrooms, however, the values rise quickly. The Federal Environment Agency therefore recommends ventilating at levels as low as 1,000 ppm. At 1,500 ppm - at the latest at 2,000 ppm - extensive ventilation is urgently required. The table below illustrates the respective CO₂ concentration limits and their influence on air quality.
If the CO₂ concentration in the room exceeds ten times the recommended limit, this can lead to nausea, shortness of breath and even unconsciousness.
air-Q Lab: Testing the ventilation concept of a classroom
We wanted to know how quickly the CO₂ concentration rises in a classroom. In our test, we used the air-Q to track the carbon dioxide content of the room air in a fully occupied classroom with 27 people in summer. The diagram here only shows the evaluation of the first two hours, as this already represents the effects of ventilation.
What does the diagram show? The yellow line represents the CO₂ measured in the classroom. Right from 8 a.m., at the beginning of the first lesson, the CO₂ level rose slowly but steadily. Until the first small break at 8:45, the value climbed up to 1,600 ppm. After that, the room was ventilated for the first time, causing the concentration to drop to about 900 ppm. In the second lesson, the CO₂ content even exceeded the values of the first lesson and grows up to 1,900 ppm. This is mainly due to the fact that the carbon dioxide concentration did not drop sufficiently during the previous ventilation. At the big break, the rooms were ventilated again, yet the concentration did not drop sufficiently here either and was still over 1,000 ppm.
The air-Q as a CO₂ traffic light
The air-Q test shows how important ventilation is at school. Although the classroom was ventilated again and again, the ventilation time was somewhat too short. Since the temperature difference between inside and outside was not yet very large at the time of the test, no rapid air exchange could take place.
To keep an eye on the air quality and the carbon dioxide content of the classroom air, the air-Q air analyser also functions as a CO₂ traffic light. The LED displays in blue, orange and red warn of too much CO₂ in the classroom, and thus also of an increase in aerosols. The coloured light display makes it easy for both teaching staff and students to see when the limit values are reached and thus a possible increased risk of infection for Corona and to take countermeasures.
We have developed the air-Q Light especially for the needs of schools and offices. With its help, it is very easy to check how efficient the ventilation is and how the ventilation concept can be adapted or expanded.
Noise measurement in the classroom
In the classroom, it not only gets stuffy quickly, but also loud. However, high sound peaks and constant noise put a strain on the hearing. A high noise level disrupts lessons, impairs receptiveness and has a stress factor effect on the organism. But it is not only performance and well-being that diminish. Noise also provokes physical effects. If, for example, the hair cells in the inner ear are permanently damaged by too loud noises in the classroom, this limits acoustic perception. Moreover, these hair cells cannot grow back. Noise-induced damage is therefore irreparable and can lead to temporary or even chronic ringing in the ears (tinnitus) as well as hearing loss.
The air-Q Light is equipped with a special sensor so that you can keep an eye on the volume as well as the room air. It can also be used as a noise meter and measure the decibels in the room. Here, too, an easy-to-understand traffic light system shows when the limit is reached. If the class is quiet, the green LEDs indicate this. If the commotion increases, this is reflected in the orange light - a warning to the class, so to speak. The red lights and an acoustic warning signal, on the other hand, make it clear that the noise level must now be drastically reduced. Even the youngest children understand this colour scale.
In this way, the air-Q not only provides all-round preventive health protection, but also ensures greater performance - for pupils and teachers.
(Cover photo: Shutterstock / Syda Productions)
