This 2001 Honda Civic was already in the shop for some other repairs and the glove box was out so I could see the cabin air filter cover and I decided to do a quick post on replacing it. Cabin air filter should be replaced as outlined in your owners manual and if you do not you may have severely restricted air flow from the vents. The following picture shows the glove box and the cabin air filter is behind it.
Open the glove box and release the side clips.
You do not have to remove the lower hush panel but I was actually reassembly the dash from another repair and had the picture.
Remove the two screws that attach the glove box hinges. One on each side. Take the glove box out of the car.
Release the retaining clip on the left side and pull the cover off.
There are two filters in the slot, grab the pull handle for the left filter and pull it out. Grab the handle for the right filter and slide the filter to the left and then pull it out.
Place the new filter for the right side in the box and slide it fully to the right. place the left filter into position.
Reinstall the cover assembly as shown below and install the glove box and you are done.