A room air filter apparatus includes a multi sided housing having longitudinally spaced first and second ends, a plurality of sides between the first and second ends, and {HEAD ~ a plenum} inside {TAIL ~ the housing} 
A room air filter apparatus includes a multi sided housing having longitudinally spaced first and second ends , a plurality of sides between the first and second ends , and { HEAD ~ a plenum } inside { TAIL ~ the housing }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL