Narrative:

At approximately XA26Z at FL310, 40-80 NM nne of cae, both the first officer and myself smelled fumes. We immediately called the flight attendant and asked whether she smelled any fumes in the cabin. She did not. The fumes smelled like propane gas which quickly became stronger and became an acrid smell. We immediately donned our oxygen masks and established communication. I declared an emergency with ATC, requested a lower altitude and vectors to the closest airport. As we descended, the fumes became stronger and more acrid. I deployed the passenger oxygen masks for their safety. The flight attendant was advised to have the passenger use the masks until we land. We landed on runway 11 at columbia, sc, and came to a stop on a high speed taxiway. I performed the memory items for 'evacuate/evacuation because of crash, severe aircraft damage or internal fire' but elected for an orderly deplaning of the passenger through the forward passenger door. I searched the cabin and then exited the aircraft. The times stated below were provided by cae crash fire rescue equipment whose source was local ATC: emergency declared at XA20Z. Landed at XA41Z. The crash fire rescue equipment confirmed the strong presence of fumes in the cockpit but could not determine its source. The next day the FAA and maintenance discovered an 8 inch crack on the first officer's right windshield, which they believe allowed moisture to contact the heating element and arc with the heating block to create the odor (fumes) we smelled.

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Original NASA ASRS Text

Title: ACRID FUMES IN COCKPIT CAUSE ACR FLC TO DECLARE EMER AND LAND AT NEAREST SUITABLE FIELD.

Narrative: AT APPROX XA26Z AT FL310, 40-80 NM NNE OF CAE, BOTH THE FO AND MYSELF SMELLED FUMES. WE IMMEDIATELY CALLED THE FLT ATTENDANT AND ASKED WHETHER SHE SMELLED ANY FUMES IN THE CABIN. SHE DID NOT. THE FUMES SMELLED LIKE PROPANE GAS WHICH QUICKLY BECAME STRONGER AND BECAME AN ACRID SMELL. WE IMMEDIATELY DONNED OUR OXYGEN MASKS AND ESTABLISHED COM. I DECLARED AN EMER WITH ATC, REQUESTED A LOWER ALT AND VECTORS TO THE CLOSEST ARPT. AS WE DSNDED, THE FUMES BECAME STRONGER AND MORE ACRID. I DEPLOYED THE PAX OXYGEN MASKS FOR THEIR SAFETY. THE FLT ATTENDANT WAS ADVISED TO HAVE THE PAX USE THE MASKS UNTIL WE LAND. WE LANDED ON RWY 11 AT COLUMBIA, SC, AND CAME TO A STOP ON A HIGH SPD TXWY. I PERFORMED THE MEMORY ITEMS FOR 'EVAC BECAUSE OF CRASH, SEVERE ACFT DAMAGE OR INTERNAL FIRE' BUT ELECTED FOR AN ORDERLY DEPLANING OF THE PAX THROUGH THE FORWARD PAX DOOR. I SEARCHED THE CABIN AND THEN EXITED THE ACFT. THE TIMES STATED BELOW WERE PROVIDED BY CAE CFR WHOSE SOURCE WAS LCL ATC: EMER DECLARED AT XA20Z. LANDED AT XA41Z. THE CFR CONFIRMED THE STRONG PRESENCE OF FUMES IN THE COCKPIT BUT COULD NOT DETERMINE ITS SOURCE. THE NEXT DAY THE FAA AND MAINT DISCOVERED AN 8 INCH CRACK ON THE FO'S R WINDSHIELD, WHICH THEY BELIEVE ALLOWED MOISTURE TO CONTACT THE HEATING ELEMENT AND ARC WITH THE HEATING BLOCK TO CREATE THE ODOR (FUMES) WE SMELLED.

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.