My purifier made a loud rattling sound as though the turbine was striking the housing on every rotation. Got a real human on the phone within seconds and she walkede through some troubleshooting, which didn't work. They shipped a new one right away.If the company is curious, the issue turned out to be a faulty nut which held the turbine to the axle. It was drilled crooked, and caused the turbine to sit askew.
We have 3 PuroAir units or our 6,000 square foot house, and by the time I need to change the filters - they are absolutely filthy. The HEPA filters pick up everything and it has really helped to keep my allergies in check.