A SF340 RETURNED TO THE GATE AFTER TAXI OUT WHEN THE CABIN FILLED WITH SMOKE AFTER THE FIRST ENGINE START OF THE DAY.

Narrative

DURING TAXI OUT FOR ZZZ WE RECEIVED A CALL FROM THE FLT ATTENDANT STATING THAT THERE WAS A FUNNY ODOR IN THE CABIN. I COULD SMELL ENG EXHAUST ODOR WHICH DOES OCCUR AFTER JUST OPENING THE BLEEDS AFTER ENG START. I ASKED HER IF WHAT SHE SMELLED WAS ENG EXHAUST. SHE SAID YES. WE COMPLETED OUR FIRST FLT OF THE DAY TEST; AND SHORTLY AFTER (LESS THAN 1 MIN) WE STARTED TO SMELL A DIFFERENT ODOR IN THE COCKPIT -- AN ELECTRICAL BURNING SMELL. WE WERE ON THE TXWY ABEAM THE GATE; AND DECIDED TO RETURN TO HAVE THE ODOR CHKED OUT. WE CALLED OPS AND TOLD THEM ABOUT OUR GATE RETURN; AND THAT WE WOULD BE DEPLANING. WE SHUT DOWN THE ACFT AND COMPLETED OUR SHUTDOWN CHKLIST. I MADE AN ANNOUNCEMENT TO THE PAX THAT THEY WOULD BE GETTING OFF THE ACFT DUE TO A MAINT ISSUE WE WOULD LIKE TO HAVE CHKED OUT. WE OPENED THE COCKPIT DOOR TO FIND THAT THE CABIN WAS FILLING WITH A HAZE; SMOKE. I CALLED ZZZ TWR AND TOLD THEM WE WOULD LIKE CFR FOR SMOKE IN THE CABIN. THE PAX DOOR WAS OPENED AND PAX WERE EXITED OFF THE AIRPLANE NORMALLY VIA THE STAIRS. THE RAMP; CUSTOMER SVC AGENTS WERE UNLOADING THE ACFT AND I INFORMED THEM THAT THERE WAS; HAD BEEN A POTENTIAL FIRE AND TO MOVE AWAY. PAX WERE MOVED INSIDE. CFR MET THE ACFT WITHIN MINS AND INSPECTED THE ACFT. I MADE A LOGBOOK ENTRY. NO QRH PROCS WERE COMPLETED; BECAUSE WE HAD NO INDICATION OF A FIRE; SMOKE IN THE FLT DECK. I DID NOT DECLARE AN ACTUAL 'EMER' BECAUSE WE WERE ON THE GND; AND HAD NOTIFIED ATC ABOUT THE SMOKE IN THE CABIN AND ASKED FOR CFR; AND WE EVACED THE ACFT WITHIN SECONDS OF CALLING THE TWR. SUPPLEMENTAL INFO FROM ACN 796708: AFTER ACFT DOOR CLOSED; I WAS DOING COMPLIANCE CHKS IN CABIN WHEN I NOTICED AN ODOR. NOTIFIED THE CAPT. CAPT SAID SOMETIMES WHEN THE ENGS FIRST START UP THERE IS AN ODOR. AFTER FLT CREW BEGAN 1ST MORNING ENG CHKS THE ODOR INCREASED AND THE ODOR CHANGED. CAPT CALLED AND SAID WE WERE GOING BACK TO THE GATE. WE RETURNED TO THE GATE AND ASKED THE PAX TO DEPLANE; TAKING ALL PERSONNEL ITEMS WITH THEM. THIS WAS DONE IN ORGANIZED MANNER.