Anyone using an air purifier for the first time quickly asks the same question: should the window be open or closed? The answer depends on what exactly you want to achieve, as an air purifier and ventilation do not perform the same task.
What an air purifier does and doesn't do
An air purifier such as the Dynter AirPure Plus PA244 draws in air, passes it through filters, and blows clean air back into the room. Particulate matter, pollen, household dust, and other particles are trapped in the HEPA13 filter. What an air purifier does not do is add fresh oxygen or remove CO2. For the latter, you simply need ventilation, such as an open window, air vent, or mechanical system.
Why a closed window often works better
If you leave the window wide open while the air purifier is running, new outside air is constantly coming in, along with everything it contains: traffic emissions, pollen during the season, or moisture during rainy weather. The air purifier then has to continuously catch up, and the measured air quality improves much more slowly. For the fastest possible effect, for example during hay fever season or after cooking, a closed room with the air purifier running works best. A device's CADR rating (which is 260 m3 per hour for the PA244) indicates how quickly the air in a closed room is refreshed.
When you still need to ventilate
Nevertheless, opening a window occasionally is not an unnecessary luxury. CO2 accumulates in a closed room, especially if several people are sleeping or working there, and you often notice this as a stuffy or tired feeling. An air purifier does not solve this, because it only filters particles out of the air that is already in the room. It is therefore wise to air out the room briefly a few times a day, preferably when the outside air is relatively clean, and then let the air purifier do its job again in a closed room.
Differences by season and situation
The right choice also varies by situation. During hay fever season, it is usually wiser to keep windows closed and rely on the air purifier, especially during the day when pollen concentrations outside are often at their highest. During a heatwave, there is another dilemma: you often want to ventilate for cooling, even if that means temporarily letting in more outside air. In winter, airing out the room briefly and effectively is usually sufficient, after which the air purifier can work for the rest of the day in a closed, well-insulated room.
A practical rule of thumb
In practice, the following approach works well for most households:
- Ventilate briefly and purposefully, for example 10 to 15 minutes, preferably at a quiet time of day.
- Close the window afterwards and let the air purifier clean the air on a higher setting.
- Switch to a lower or quiet setting during prolonged use, such as at night.
- During a pollen peak or smog warning, it is better to keep the windows closed and let the air purifier do the heavy lifting.
Our advice
If you want both healthy ventilation and effective air purification, combine brief, targeted airing with an air purifier that is powerful enough for your room. In our experience, the AirPure Plus PA244 is a pleasant choice for this: with a CADR of 260 m3/h, it is suitable for up to 55 m2, it has a HEPA13 filter that removes 99.97 percent of particulate matter, pollen, bacteria, and viruses from the air, and with the sleep timer and night mode, you can effortlessly switch back to a quiet evening mode as soon as the windows are closed again.