Sensibo Pure Filter What particle sizes are filtered by the Pure? Particles as small as 0.1um (more than 100 times thinner than human hair) are filtered by the HEPA filter of the Sensibo Pure. This includes contaminants such as bacteria and viruses, as well as PM (particulate matter) PM1.0, PM2.5 and PM10. Additionally, the active carbon filter absorbs atoms of harmful gases such as smoke and VOCs (Volatile Organic Components). Why can't I just clean the filter instead of replacing it? It's a good practice to clean the filter from time to time with a wet wipe on the outside surface. However, the internal HEPA & Active Carbon filtration system is very delicate and cannot be cleaned, so it needs to be replaced to ensure the same level of purification. Our filters incorporate a carbon filter that traps odour molecules through a process called absorption. Basically, these molecules attach to the outside of a surface, rather than being soaked into it.