Fine particulates are tiny dust particles smaller than 10 micrometres (µm) that you can't see with the naked eye, but which still affect the air you breathe. A particulate matter sensor makes this invisible air pollution visible: the device measures the amount of (fine) dust particles in the air, expressed in PM (Particulate Matter), giving you a simple and clear insight into the air quality in a given space. That way, you know exactly when it's time to ventilate, and you protect your own health and that of others. Good particulate matter sensors often have multiple functions, measuring not only particles below 10 µm but also below 2.5 µm, as well as CO2, humidity and other volatile gases.