We live in a beautiful place with mountains in our front yard and 3 dirt roads to get to the paved highway. Spring and Fall winds are epic with 45 to 70 mph wind gusts. There is fine powdery dirt in the air. We had two BLUEAIR 211's in our house for 8 years and they handled the tough conditions. I wanted something that had a smaller foot print so tried out another brand that makes vacuum cleaners I like. I bought a large one for the great room and a smaller one for the bedroom. They were DEAD in 3 months, even the one that said "no-change filter." I immediately went back to BLUE AIR and it was like coming home. Immediately the air in the whole house got better and the Blue Signature is perfect for the Great Room and the 311 in the bedroom is the right size. I LOVE BLUEAIR and can say that we have given it the Big Test in a stressful environment and this brand delivers on all of its promises. The more subtle, neutral colors for the pre-filters are much appreciated. The washable pre-filter makes a very big difference. Saturday is wash day and I pop the second pre-filter on while the used one is in the wash.