This air purifier is very high tech and innovative. I have had a few over the years but none that have a colored light that changes colors with the air quality. So far it's only changed once when my husband burnt some food, and it went yellow. It also kicked into higher gear when we cooked bacon too, and I could hear it working harder to filter the air even though it's at the opposite end of the downstairs, it could still sense the air change. So far I love it! Super useful and easy to use.