AC6606 and AC6608 have NanoProtect Pro S3 filter;
The NanoProtect Pro S3 filter is designed for superior purification efficiency and lifetime against airborne particles. Multi-layer integrated filter for all-in-one 360 protection. The ever-finer filter effectively removes ultrafine particle as small as 20nm, more than 100X smaller than PM2.5, including bacteria and some viruses. High efficiency purification removes 99.97% 0.3µm particles , dense and thick filter for 50% longer lifetime.