Use the Merv 13 Filter on my household Box Fans. Not my Furnace. Just a residential home, and not recommended to go above a Merv 8 on a regular furnace. However, I attach the 2 Merv 13 Filters to 2 Box Fans (separately) and set them in my home to filter the air. I saw this type of project on "Ask This Old House" on PBS. Really cleans the household air. Dust has been greatly reduced.