Many air purifiers have a colored light or light ring that shows at a glance how clean the air in the room is. It's convenient, but what those colors exactly mean can vary by brand. Below, you can read how such a system usually works.
How the sensor determines a color
Inside the device is a particulate matter sensor that continuously measures how many particles are floating in the air, usually expressed as an index for particulate matter (PM2.5 and PM10). This measurement value is translated into a color code, so you don't have to interpret the figures yourself. As soon as the air changes, for example, because of cooking or an open window, the color switches accordingly.
The most common color meanings
- Blue or green: the air quality is good; little particulate matter has been measured.
- Yellow or orange: the air quality is moderate; more particulate matter is present than usual.
- Red: the air quality is poor; the device often automatically switches to a higher setting to improve this.
With the AirPure Plus PA244, the indicator works in the same way: the color gives an immediate impression of the current air quality, so you can see if the device is working for a good reason or if the air is already clean.
Why the color sometimes changes without an obvious reason
Particulate matter sensors are sensitive, and that is exactly what they are supposed to be. Cooking, vacuuming, lighting a candle, bringing in outdoor air, or even perfume can temporarily cause the color to change to yellow or red. After a few minutes of filtering, the value usually drops back to green or blue. That is not a malfunction; that is the system doing exactly what it is intended for.
What if the color stays red constantly
If the indicator stays red for a long time while there is no obvious source of pollution, check the filter first. A saturated filter can actually contribute to reduced air quality instead of improving it, and the sensor can also become clogged with dust, making the measurement less reliable. Gently wiping the sensor and checking the filter will solve this in most cases.
Use the color as a guideline, not an exact measurement
The color codes are intended to give an impression at a glance, not to read exact PM2.5 values as a professional air quality meter does. For most households, that is more than sufficient: you see immediately whether it is worth ventilating, or whether the air is already fine.
Our advice: keep the automatic mode on if your device has one; the air purifier will then regulate how hard it needs to work based on the measured color. If you are unsure whether the sensor of your AirPure Plus PA244 is still measuring correctly, first check whether the HEPA13 filter is due for replacement, as a clean filter also provides the sensor with a more reliable measurement to work with.
Do not confuse the color indicator with a CO2 measurement
A common misconception is that the color on an air purifier also says something about the CO2 content in the room. That is not the case: an air purifier measures and processes particulate matter, not CO2, and therefore cannot resolve a high CO2 level. If the room continues to feel stuffy while the color indicator is simply green or blue, that says something about dust particles, not about the amount of fresh air. For CO2, only ventilation helps, regardless of what color your air purifier is showing at that moment.