Over time your air ducts are going to collect dust. It’s unavoidable, just like your furniture and everything else in the home. And while you can dust and sweep up around the house, your ducts just get dirtier and dirtier. If you’re able to, you can take a peek and see if it’s time to clean them. Otherwise, keep an eye out for common signs: You’re seeing far more dust around the house than usual, even after cleaning. There are noticeable odors coming from the vents when you turn on the HVAC system. You notice your air filters are getting too dirty, too quickly. You’re seeing a mold or rodent infestation! You’ve noticed actual dust simply coming out of your vents.