What was found
FLIGHT 4245. AT FLIGHT LEVEL 250, COCKPIT HAZY WITH SMOKE AND FLIGHT ATTENDANT CONFIRMED SMOKE IN CABIN. PERFORMED EPC AND SMOKE DISSIPATED. DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. CFR DECLARED AIRCRAFT SAFE. DETERMINED PACK ONE INTERNAL FAILURE. ENERGIZED PACK ONE ONLY BLOWING HOT AIR. PRESSURE OPS CHECKED IAW AMM 21-60-00. CHECKED GOOD. REMVOED AND REPLACED LEFT ACM IAW AMM 21-51-03. OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.