Narrative:

I was flying from xyz to ZZZ when approximately 150 mi from ZZZ while descending from FL250 to FL210 we both noticed smoke entering the cockpit from the floor vents, the smell of smoke and an ashy substance coming into the cockpit. At the same time the flight attendant called from the cabin to notify us that smoke was entering the cabin. I declared an emergency and requested vectors to the closest airport for landing. We both performed our smoke in the cabin and cockpit procedures and emergency procedures. We were vectored to ZZZ while the flight attendant prepared the cabin for an emergency landing. We were vectored to the airport and landed. After landing we stopped on the runway and asked the crash fire rescue equipment to inspect the aircraft for any fire or damage. They cleared the aircraft and we taxied to the terminal under our own power where the passenger were deplaned using a stair/ramp. There were no injuries or damage to the aircraft. Callback conversation with reporter revealed the following information: the reporter stated while descending the smoke and ash entered the cockpit and the cabin attendant reported the forward cabin had smoke. The reporter said an emergency was declared and a diversion started. The reporter stated the crew noted the left pack overheat warning light was on and the pack was inoperative. The reporter said that on the ground maintenance found the left pack air cycle machine had completely come apart allowing high pressure engine bleed air to blow oil and insulation into the air conditioning ducting. The reporter stated the source of the 14TH stage air was the automatic icing system detecting ice and switching from 9TH stage air to 14TH stage high pressure engine bleed.

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Original NASA ASRS Text

Title: AN EMB135 IN DSCNT FROM FL250 TO FL210 DECLARED AN EMER AND DIVERTED DUE TO SMOKE AND ASHY SUBSTANCE COMING INTO THE COCKPIT AND CABIN.

Narrative: I WAS FLYING FROM XYZ TO ZZZ WHEN APPROX 150 MI FROM ZZZ WHILE DSNDING FROM FL250 TO FL210 WE BOTH NOTICED SMOKE ENTERING THE COCKPIT FROM THE FLOOR VENTS, THE SMELL OF SMOKE AND AN ASHY SUBSTANCE COMING INTO THE COCKPIT. AT THE SAME TIME THE FLT ATTENDANT CALLED FROM THE CABIN TO NOTIFY US THAT SMOKE WAS ENTERING THE CABIN. I DECLARED AN EMER AND REQUESTED VECTORS TO THE CLOSEST ARPT FOR LNDG. WE BOTH PERFORMED OUR SMOKE IN THE CABIN AND COCKPIT PROCS AND EMER PROCS. WE WERE VECTORED TO ZZZ WHILE THE FA PREPARED THE CABIN FOR AN EMER LNDG. WE WERE VECTORED TO THE ARPT AND LANDED. AFTER LNDG WE STOPPED ON THE RWY AND ASKED THE CFR TO INSPECT THE ACFT FOR ANY FIRE OR DAMAGE. THEY CLRED THE ACFT AND WE TAXIED TO THE TERMINAL UNDER OUR OWN PWR WHERE THE PAX WERE DEPLANED USING A STAIR/RAMP. THERE WERE NO INJURIES OR DAMAGE TO THE ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED WHILE DSNDING THE SMOKE AND ASH ENTERED THE COCKPIT AND THE CABIN ATTENDANT RPTED THE FORWARD CABIN HAD SMOKE. THE RPTR SAID AN EMER WAS DECLARED AND A DIVERSION STARTED. THE RPTR STATED THE CREW NOTED THE L PACK OVERHEAT WARNING LIGHT WAS ON AND THE PACK WAS INOPERATIVE. THE RPTR SAID THAT ON THE GND MAINT FOUND THE L PACK AIR CYCLE MACHINE HAD COMPLETELY COME APART ALLOWING HIGH PRESSURE ENGINE BLEED AIR TO BLOW OIL AND INSULATION INTO THE AIR CONDITIONING DUCTING. THE RPTR STATED THE SOURCE OF THE 14TH STAGE AIR WAS THE AUTO ICING SYSTEM DETECTING ICE AND SWITCHING FROM 9TH STAGE AIR TO 14TH STAGE HIGH PRESSURE ENGINE BLEED.

Data retrieved from NASA's ASRS site as of July 2007 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.