We are putting an addition on our house and as you might guess, it's a bit dusty... especially at the drywall stage. I hadn't plugged our air purifier in yet when I noticed a thin layer of dust on all my granite counter tops. I cleaned them all up then plugged it in, right in front of the doorway leading to the construction. That was two days ago and as of this moment, there's been no more dust on my counter tops! This machine is amazing.