Study: Taking a closer look at the air quality in classrooms

After almost two months of asking local schools for permission to install air quality monitors in their classrooms, on the 4th of December, a local school decided to grant me access.

In my city, Almeria, Spain, there are about 110 schools. I didn’t apply to all of them because each time I managed to find a way to contact them, I had to arrange a meeting in order to explain to them what I wanted to do, and all this process takes time. I managed to contact nine schools.

For this study, schools didn’t have to pay anything, so money wasn’t the issue for their refusal. They were worried about what will happen if the results were disappointing and negative. I tried to explain to them that the aim of the study is to understand what is going on in the classroom, in real conditions, with real students. I don’t want to discredit the school either the local authorities that manage the budget for the school. For this reason, I will keep the name of the school private.


The monitors that I have installed for the study are made by Airthings. There are two Wave Plus, which include a CO2 sensor by Senseair. The sensor is called Sunrise, and it is an ultra-low-power, high precision NDIR sensor. Accuracy (CO2) ±30 ppm ±3% of reading. Finally, it features a self-correction system that allows them to auto-calibrate every 180 hours. I also have included a Wave mini monitor in the teacher’s office room. 

One of the reasons I have selected the business solution from Airthings is that they can communicate with the Hub over great distances. They offer great security as I don’t have the devices connected to the school WiFi network, but it uses a cellular connexion in order to make sure data flow constantly. The distance between the Hub and the Wave Plus monitors is about 65 meters, and 4 walls are between them.

Another reason that I have selected this solution is that it offers advanced tools for me via the dashboard and the app, but also it allows students and teachers to check the indoor AQ with the QR codes that I have generated for them. Each device has a different QR code with easy to read information.


The set up is simple, I didn’t have many indoor air quality monitors, so I told them that I need two classrooms, one from a primary school (8-9 years old) and a second one from a secondary school (10-11 years old). I also included one monitor in the teacher’s office room.

The first classroom is 45,8m2, and the height of the room is 2,5m which gives us 114,5m3. The room is occupied by 26 students. The second classroom is 47,7m2, and the height of the room is 3m which gives us 143,1m3. It is occupied by 31 students. At least that was the number of individual desks in the rooms.

The primary indoor pollutant that I am going to measure is carbon dioxide (CO2). However, I can measure tVOC, Radon, temperature, humidity, atmospheric pressure, and in one of the classrooms I included a Particulate Matter (PM2.5) sensor too.

The Study

The climate in Almeria is mild and opposite to other cities in northern Europe or even northern Spain where temperatures drop below 0ºC, here temperatures don’t drop below 8ºC in winter outdoors.

According to the Köppen climate classification, Almeria is considered to have a hot semi-arid climate (BSh). As a result, I want to see if schools and other indoor environments can keep ventilation rates optimal and CO2 concentrations below 1000 ppm. Most houses and schools here in Almeria don’t have HVAC or HRV systems, and they rely on natural ventilation − open windows.

KöppenGeigers Climate Classification in Almeria, Spain

Many people became aware of the Indoor Air Quality and Ventilation needs of buildings during the pandemic of COVID-19. However, it is important to keep in mind that indoor air quality is essential for our health with or without COVID-19. High concentrations of CO2 are directly correlated to impact our cognitive abilities − the way we think. Productivity in classrooms and offices is an essential key to render great results.

Will schools be able to keep CO2 concentrations low? Does the local climate promote healthy indoor environments or are HVAC/HRV systems necessary to ensure optimal ventilation rates without losing heat and comfort? Some of the questions this study will try to answer.


4 thoughts on “Study: Taking a closer look at the air quality in classrooms

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s