I have had the Alen flex for just under two years. I bought it when there were local forest fires and the air was terrible. Now I run it intermittently but it does get a fair amount of use. No pets, no smoking, 1000 sq ft apartment.

Recently I ordered a new filter. The last replacement was 15 months ago. I got curious and wanted to take some measurements. The used filter weighed 790 grams and the new one weighed 694 grams. The filters were identical and the part numbers were exactly the same. That means that the used filter collected ~100 grams of particulate and dust. That is about the weight of three 9V batteries. I am pretty satisfied with that performance.

I am just an average curious customer.