I researched every air purifier I could find for six months. For some it is an expensive purchase not taken lightly. I made the correct choice with my Air Doctor. After just 24 hours I came after being out all day and new something was different, the air in my home felt light and "fresh". I am very happy with my purchase after a one month review.
The Air Doctor runs quietly on low until I start cooking or doing something which kicks it into a higher gear. It clears the air quickly and resumes on low.