What a difference the 75i has made in our home. Although our home is only 1717 sf. we are so glad we went with this top model. We spent hours and hours researching and so thankful with our decision going with Alen. The unit is very quiet it doesn't bother us at all in the bedroom. We have two dobermans and the pet filter has help with pet orders. Love the auto function and yes it does work. Thanks Alen.