I can tell this machine is working well as there is very little dust on my furniture. I usually dust 2-3 times a day. BUT that is not the best part. my allergies inside have calmed down and I am not sneezing and coughing . Even when I go outside for awhile and come back in I may be congest for a short time but the symptoms vanish quickly. I am so please with this unit. I just wish I had purchased a long time ago. Would have saved me much sneezing and coughing.