What was found
PDX FLIGHT NR 2156 EN ROUTE EUG TO SEA, JUST PASSING PDX, CAPTAIN AND FO SMELLED SMOKE, FLIGHT ATTENDANT MENTIONED HAZE IN THE CABIN, ESPECIALLY NEAR THE REAR OF THE AIRCRAFT. RAN APPROPRIATE CHECKLIST. BLEED NR 1 ON AND BLEED NR 2 OFF SEEMED TO CLEAR SMOKE. NORMAL LANDING. FIRST SMELLED SMOKE AT 22,000 FEET. MAINTENANCE REPLACED THE NR 2 OIL BREATHER TUBE CARBON SEAL. OPERATIONAL CHECK FLIGHT GOOD. AIRCRAFT RETURNED TO SERVICE.