DC10 RETURNS TO GATE DUE TO NOXIOUS FUMES ON FLT DECK.

Narrative

FOLLOWING A NORMAL PREFLT; ENG START; AND INITIAL TAXI OUT; EVERYTHING WAS NORMAL. JUST PRIOR TO TKOF; WE STARTED TO SMELL A SLIGHT BURNING TYPE SMELL IN THE COCKPIT. WE INITIALLY THOUGHT IT WAS FROM A SEWAGE TREATMENT PLANT LOCATED NEARBY. THE ACFT WAS THEN CLRED FOR TKOF ON RWY XX. WE TAXIED ONTO THE RWY AND AGREED AS A CREW THAT THE SMELL WAS A LOT STRONGER AND SMELLED LIKE SOMETHING WAS BURNING. WE NOTIFIED TWR WE'D LIKE TO TAXI OFF THE RWY AND INVESTIGATE THE FUMES. TWR INITIALLY TOLD US TO TAXI CLRNC; AND THEN TOLD US TO TAXI DOWN THE RWY TO CLR AT TXWY X. AT THIS TIME THE CAPT DIRECTED THE CREW TO DON OUR OXYGEN MASKS AND SMOKE GOGGLES. THE APPROPRIATE PHASE 1 WAS ACCOMPLISHED TO INCLUDE INFORMING OUR JUMPSEATER TO DON HIS MASK. I WANT TO NOTE THAT THE THROTTLES WERE NEVER ADVANCED FOR A TKOF AND THE TWR ASKED US IMMEDIATELY IF WE NEEDED ASSISTANCE. WE THEN DECIDED THE BEST COURSE OF ACTION WOULD BE TO CONTINUE BACK TO OUR RAMP AND LET MAINT INVESTIGATE THE PROB. WE WERE GIVEN A QUICK TAXI BACK TO OUR RAMP. UPON REACHING TXWY XX; WE DETERMINED THAT THE FUMES WERE MUCH MORE INTENSE AND THE CAPT DIRECTED ME TO CALL OUT THE FIRE TRUCKS. I'M NOT SURE IF I EVER DECLARED AN EMER; BUT I DID REQUEST THE FIRE TRUCKS AND STATED WE THOUGHT WE MIGHT HAVE SOMETHING BURNING. THE TRUCKS RESPONDED IMMEDIATELY AND MET US ABEAM OUR GATE. WE RAN THE EMER EVAC CHKLIST AND SPOKE WITH THE FIRE DEPT ON A DISCRETE FREQ. OUR INTENTION WAS TO EGRESS VIA OUR CREW STAIRS; BUT THEY WERE SLOW IN BRINGING THEM OUT TO THE ACFT AND THE FIRE DEPT REQUESTED WE POP THE SLIDE. THE EVAC CHKLIST WAS FINISHED AND WE EGRESSED VIA THE SLIDE ON THE L1 DOOR. AS OF WRITING THIS; THE CAUSE OF THE BURNING SMELL COULD NOT BE 100% IDENTED. THERE WAS A SKYDROL LEAK FOUND IN THE MAIN GEAR AREA AND THE FLT ENGINEER'S SEAT MAY HAVE MALFUNCTIONED AND OVERHEATED. THE PLANE WAS BEING LOOKED AT WHEN I LEFT ZZZ A FEW HRS LATER.