DIY Cost: $ 10 - 20 Est. Time: 10 mins Difficulty: Easy Summary Step-by-step instructions on how to replace the cabin air filter on a 2016-2020 Kia Optima. What you will need Cabin air filter (Kia Optima) Procedure Unlock the vehicle and open the passenger door. Open the glove box located above the front-seat passenger's footwell. Twist the tabs inside the glove box counterclockwise to unlock them. Pull out the clamp on the right side of the glove box to access the cabin air filter. Squeeze the tab on the right side of the cabin air filter cover and remove it from the housing. Pull the cabin air filter out. Install the new cabin air filter by pushing it to its place. Note the direction of the airflow, the air filter should have an arrow on the side. Reinstall the cover of the cabin air filter. Line it up back to the cabin air filter box and push it to lock in place. Hook the clamp back to the glove box. Line up the tab back to the glove box and twist it clockwise to lock it. Close the glove box.