Recently Portland Oregon was rated he worst air quality in the world due to local fires in Oregon and California. I had purchased two blue air 411’s one month prior and I can’t express how thankful I was that I did that. during that horrific experience the 411 units kept my home free from smoke particles. When I change the filter It was caked with smoke residue and I thought to myself that could’ve been in my lungs. Thank you blue air for the simple yet highly effective product