I was hopeful, but never really expected the results that I’ve received with the 75i and the 45i that I recently purchased. I have had terrible sinus congestion for more years than I can remember, and take two nasal prescriptions daily. Even with that, I went through a box of tissues every couple of days. Within 24 hours after the two purifiers were employed, I’ve rarely needed a tissue to clear my sinus. I will be purchasing a third unit because of the insidious smoke that is being created from the west coast fires. Also very impressed by the warranty and the quiet level of the fan.