Narrative:

Cruising at FL350 in icing conditions with engine and airfoil anti-ice on; 'pressurization flow' light illuminated along with an initially slow cabin climb. A quick check around the cockpit showed all other indications normal. We requested and received a lower altitude from ATC; but almost immediately the cabin began climbing rapidly. Declared emergency; requested 10000 ft; accomplished checklist. Cabin never climbed above 10000 ft; oxygen masks did not drop in cabin. There were thunderstorms in the area; we got continuous moderate turbulence at 10000 ft and it did not smooth out until about 40 mi or so from ZZZ at 8000 ft. A passenger requested paramedics at the gate; was feeling ill from what I believe to be the bumpy ride. Couple additional comments in regards to the event. Initially; when we first started to lose the cabin; it appeared that both packs were operating normally. After we started the emergency descent; I really didn't look at them again as I was concentrating on just getting down to a habitable altitude as quickly and safely as possible. Additionally; somewhere between 18000 ft and 15000 ft or so the autoplt disengaged; probably due to the turbulence. I ended up hand-flying the aircraft most of the way to ZZZ after that. Once it smoothed out; tried the autoplt again and it stayed engaged. It has also occurred to me that I believe we never asked ATC to notify the company; lots of things going on. When we finally arrived at the gate; the agent was surprised that we had been an emergency aircraft. Next time; if another emergency happens; I will try to notify somebody; time and conditions permitting.

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Original NASA ASRS Text

Title: MD80 FLT CREW EXPERIENCES LOW FLOW AT FL350 WITH WING AND ENG ANTI-ICE ON. CABIN ALT BEGINS TO CLB AND AN EMER DSCNT IS INITIATED WITH LNDG AT DEST ARPT.

Narrative: CRUISING AT FL350 IN ICING CONDITIONS WITH ENG AND AIRFOIL ANTI-ICE ON; 'PRESSURIZATION FLOW' LIGHT ILLUMINATED ALONG WITH AN INITIALLY SLOW CABIN CLB. A QUICK CHK AROUND THE COCKPIT SHOWED ALL OTHER INDICATIONS NORMAL. WE REQUESTED AND RECEIVED A LOWER ALT FROM ATC; BUT ALMOST IMMEDIATELY THE CABIN BEGAN CLBING RAPIDLY. DECLARED EMER; REQUESTED 10000 FT; ACCOMPLISHED CHKLIST. CABIN NEVER CLBED ABOVE 10000 FT; OXYGEN MASKS DID NOT DROP IN CABIN. THERE WERE TSTMS IN THE AREA; WE GOT CONTINUOUS MODERATE TURB AT 10000 FT AND IT DID NOT SMOOTH OUT UNTIL ABOUT 40 MI OR SO FROM ZZZ AT 8000 FT. A PAX REQUESTED PARAMEDICS AT THE GATE; WAS FEELING ILL FROM WHAT I BELIEVE TO BE THE BUMPY RIDE. COUPLE ADDITIONAL COMMENTS IN REGARDS TO THE EVENT. INITIALLY; WHEN WE FIRST STARTED TO LOSE THE CABIN; IT APPEARED THAT BOTH PACKS WERE OPERATING NORMALLY. AFTER WE STARTED THE EMER DSCNT; I REALLY DIDN'T LOOK AT THEM AGAIN AS I WAS CONCENTRATING ON JUST GETTING DOWN TO A HABITABLE ALT AS QUICKLY AND SAFELY AS POSSIBLE. ADDITIONALLY; SOMEWHERE BTWN 18000 FT AND 15000 FT OR SO THE AUTOPLT DISENGAGED; PROBABLY DUE TO THE TURB. I ENDED UP HAND-FLYING THE ACFT MOST OF THE WAY TO ZZZ AFTER THAT. ONCE IT SMOOTHED OUT; TRIED THE AUTOPLT AGAIN AND IT STAYED ENGAGED. IT HAS ALSO OCCURRED TO ME THAT I BELIEVE WE NEVER ASKED ATC TO NOTIFY THE COMPANY; LOTS OF THINGS GOING ON. WHEN WE FINALLY ARRIVED AT THE GATE; THE AGENT WAS SURPRISED THAT WE HAD BEEN AN EMER ACFT. NEXT TIME; IF ANOTHER EMER HAPPENS; I WILL TRY TO NOTIFY SOMEBODY; TIME AND CONDITIONS PERMITTING.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.