Got both the 1000 and 2000 series from Philips, and even though we were skeptical whether they worked, the air has been so bad lately in Australia that we had to do something. And YES, we noticed a difference. We tested it too .. it was reading "good" air inside, but it was smokey outside, so we opened the door for less than a minute and the Philips went into overdrive immediately sensing the smoke we'd just let in. So happy and would absolutely recommend this brand for air purifying.