BE90 FLT CREW SUFFERS SMOKE IN CABIN AND COCKPIT AND CONSIDERS AN OFF AIRPORT EMERGENCY LANDING. ATTEMPT IS ABANDONED WHEN SMOKE FINALLY DISSIPATES AND THEY PROCEED TO THE NEAREST SUITABLE AIRPORT FOR A SAFE LANDING.

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PAX REQUESTED THAT CABIN TEMP BE INCREASED. CABIN TEMP KNOB WAS INCREASED TO THE 6 O'CLOCK POS. SMELL OF SMOKE WAS APPARENT A FEW MINS LATER. IT THEN PROGRESSED TO VISUAL WHITE SMOKE COMING OUT BENEATH THE PLT AND COPLT SUB-PANEL. IN ADDITION; ONE OF THE PAX ALERTED THE PIC OF SMOKE COMING OUT OF THE FLOORBOARD NEAR THE WING SPAR. OXYGEN WAS DONNED AND EMER WAS DECLARED WITH CTR. EMER DSCNT WAS CLRED TO 12000 FT. ON THE DSCNT; THE BLEED WAS TURNED OFF IN AN ATTEMPT TO ELIMINATE THE SMOKE COMING INTO THE COCKPIT. TO INCREASE COCKPIT VISIBILITY; THE CABIN WAS PLACED ON DUMP MODE AT 15000 FT. SMOKE WAS STILL ENTERING THE COCKPIT AND CABIN DESPITE ALL ATTEMPTS. THE BATTERY; GENERATORS; AND INVERTER WERE TURNED OFF IN A FURTHER ATTEMPT TO EXTINGUISH THE SOURCE OF SMOKE IF IT WERE ELECTRICALLY RELATED. FOR FEAR THAT THE SITUATION WOULD ESCALATE INTO FIRE; THE PIC DSNDED BELOW 12000 FT IN AN ATTEMPT TO LAND OFF FIELD. A DIRT FIELD WAS SELECTED AND ON FINAL; THE APCH WAS ABANDONED DUE TO PWR LINES AND FENCES. AS THE PLANE WAS LEVELED OFF; IT WAS NOTICEABLE THAT THE SMOKE WAS NO LONGER ENTERING THE COCKPIT AND CABIN. PIC CLBED TO A SAFE ALT AND DECIDED TO REINITIATE ATC COM. THE BATTERY WAS TURNED ON FIRST. STILL WITHOUT LUCK IN GETTING THE WORD IN WITH CTR; THE OTHER GENERATOR WAS TURNED ON. FINALLY; COM WAS RE-ESTABLISHED WITH CTR. THE PIC REQUESTED ATC FOR THE NEAREST ARPT. ATC ADVISED OF ZZZ WHICH WAS LOCATED 30 MI TO THE E (GPS BEARING OF 115 DEGS). THE PLANE LANDED AT ZZZ SAFELY. MAINT IDENTED THE SOURCE OF SMOKE IN THE COCKPIT AND FORWARD CABIN WAS CAUSED BY A BURNT BLOWER MOTOR UNDER THE PLT SEAT. UNDER NORMAL CONDITIONS; THE BLOWER TURNS ON WHEN ADDITIONAL HEAT IS REQUIRED AS ADJUSTED BY THE CABIN TEMP RHEOSTAT. THE SITUATION COULD POSSIBLY HAVE BEEN REMEDIED EARLY ON; HAD THE RHEOSTAT BEEN TURNED DOWN AT THE FIRST SIGN OF SMOKE (SENSE OF SMELL).