Hello, this is Ava with Think Crucial.
There are 3 settings for optimum air filtration. You can operate your Holmes air purifier continuously on the Medium (2) setting. It's rugged motor has been designed to give many years of use. For quieter operation (such as bedroom), select the Low (1) setting. When high levels of air polution are present, select the HIGH (3) setting to quickly circulate and filter the room air.
You can purchase a wide variety of high quality Holmes replacement parts for your Holmes Air Purifier direct from Think Crucial with free shipping and an exclusive 10% coupon for Fixya.com readers, use code: FIXYA10
I hope this was helpful.
Think Crucial Customer Care