This asks for ventilation, but is natural ventilation enough?
With natural ventilation you can open the windows to get fresh air. It works fine but has its limits. For example, in a school class with relatively many people in a limited space, the windows will typically be opened during the breaks. In this way, the CO2-concentration will rise again quickly when the windows are shut and the class resume. Furthermore, it costs on the heating bill to open the windows when it is cold outside.
With mechanical ventilation, like the Airmaster decentral ventilation units, you have two advantages immediately; First of all, you can obtain a CONSTANT level of good air quality and secondly, you save money on the heating. The Airmaster ventilation units have a very high degree of heat recovery, meaning the heat from the room is transferred to fresh air.
How do you measure the air quality?
With Airmaster mechanical decentral ventilation, you can measure and even control the ventilation with a CO2-sensor. Most commonly the control is done with a combination of timer and CO2-sensors. This way you obtain demand-controlled ventilation, meaning you get the best possible indoor climate, at a low cost.