When Was the Last Time You Checked Your Furnace Filter? by Brian Stack | Sep 8, 2017 | Furnace system, Furnaces, Service & Maintenance | 0 comments What does a furnace filter look like when it needs to be replaced? How often should you change them? Watch our newest video for answers to your furnace filter questions. Submit a Comment Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website Save my name, email, and website in this browser for the next time I comment.