Hi there, it's probably in the ceiling grill and is thin foam. Mine has a plastic screw-latch to remove the grill to get at it. It should be cleaned about once a week w/ usage. I take a lint roller to it and then wash w/ soap and hot water, then air dry. Also bought some back-up filter material at Wal Mart in case the original rips.
Mike, Kim, and Pepper
(Min Pin security)
Current TT: 2012 Eagle Super Lite 308RETS
Current Hitch: Equal-i-zer 1400/14K
Current TV: 2010 Chevy 2500HD, CC, LB, Duramax/Allison