The Deep Cleaning Project I Ignored for 12 Years: How to Clean Air Vents (and Fix Ceiling Streaks!)

I have a confession: we lived in our house for 12 years before I realized our ceiling air vents had never been deep cleaned. Here is the exact step-by-step guide to removing HVAC registers and cleaning those ugly gray ceiling streaks, and a quick DIY trick to make old vents look brand new.