Cabin air filter.

Here is a guide to show you what you are in for when doing the job and the instructions from the manual below.

https://www.2carpros.com/articles/how-to-change-an-air-cabin-filter

Cabin Air Filter

A cabin air filter is available as standard equipment on dual-zone EATC vehicles. Electronic Manual Temperature Control (EMTC) vehicles are not equipped from the factory with a cabin air filter, but are equipped with a screen in place of the filter to prevent any large foreign material from entering the heater core and evaporator core housing. The cabin air filter or screen can be accessed by removing the glove compartment and removing the cabin air filter access cover.

A cabin air filter can be installed as a dealer accessory on vehicles not originally equipped with a filter, but only a screen or a filter should be installed, never both.

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Cheers