Blueair Genuine Classic 500/600 Series Replacement SmokeStop Carbon Filter for 605, 680i Air Purifier – HEPASilent Activated Carbon Reduces VOCs, Odours, Chemicals

I've been using the Blueair 501 with somokestop filters for a few years now. It is absolutely brilliant. And amazing at removing everything airborne! Smoke, smells etc. and you don't get much dust settling! I have a perfume allergy (and smoke) and it's been great for for me.The drawback is, of course, cost. I replace my filters about 3 times a year. It would probably be more efficient to do it 4 times a year.So work out if your happy with the yearly running cost before you buy.

The bottom filter is the “as new” filter I received from Amazon, obviously I did not use it as this is clearly a health hazard.The top filter is one I purchased from a reputable retailer.

These are (the inferior) Particle Filters not SmokeStop filters.

I would be very interested to know what is the chemical formula for Magnesium Dioxide which, in this manufacturer's description it is claimed is included in the filters as one reason for their excellent performance (see "Hundreds of activated carbon pellets impregnated with magnesium dioxide...…" etc.)It is unfortunate that these expensive filters are over-claimed because the BlueAir product itself seems good quality.