What was found
CABIN ALTITUDE HAD SLOW CONTINUOUS CLIMB, REACHING 9820FT AT FL290. BEGAN IMMEDIATE DESCENT TO 10000FT. MASKS DID NOT DROP. RETURNED TO DTW, LANDING EVENTFULLY. REPLACED CPC NR 1, AND STRUCTURAL LEAKAGE CHECK ACCOMPLISHED (SECURED PACK CONDENSOR BELLOWS, ADJUSTED OVERWING DOOR SEAL ON L/P 6839104), CHECKS OK FOR SERVICE.