I wanted to give this thing a fair trial. Being in the kitchen it kept reading 0% clean air. It was near the litterbox so we gave it a pass. Our closet has had a smell since we installed shelves so I figured a small enclosed space would be an easy test to see how well it works. We have an air quality sensor that we compared it to. As you can see the ACTUAL particals per million are far less than the Shark purifier reads. It has been in there for a full month and the “air quality” has not changed. There also is still a woody smell from the shelves. So not only is the sensor absolute garbage, so is the purifier itself. DO NOT PURCHASE THIS. *I was given this product for free by Influenster in exchange for my honest review.