MD80 FLT CREW REPORTS AIR CONDITIONING SMOKE IN THE CABIN DURING GROUND HOLD AT LAS. FLT CREW IS UNABLE TO CLEAR SMOKE AND RETURNS TO GATE WHERE PASSENGERS ARE EVACUATED THROUGH DOOR L1 AND REAR AIR STAIR.

Narrative

WE WERE TAXIING OUT IN LAS. THERE HAD BEEN A GND STOP EARLIER DUE TO WX PASSING OVER THE ARPT. AS A RESULT THERE WERE MANY ACFT ON FREQ. WE WERE ON TXWY B JUST SHORT OF C3. WHILE FACING E WE HAD A DIRECT TAILWIND OF 15 KTS GUSTING TO 30 KTS. TO HELP COOL THE FULL CABIN WE HAD THE APU AIR ON WITH THE L XFEED OPEN. THE ACFT WAS STOPPED AND THE CAPT NOTED THAT THE AIR FROM THE PACKS STARTED TO SMELL 'HOT.' IT WAS THE SMELL IN MY EXPERIENCE OF WHEN THE SYS IS WORKING HARD TO COOL THE CABIN AND THE DUCTS OR SOME OTHER PART HEATS UP. RIGHT AFTER THAT THE FLT ATTENDANTS CALLED AND RPTED SMOKE IN THE CABIN. CAPT TURNED THE APU AIR AND THE PACKS OFF. WE BRIEFLY DISCUSSED THE POSSIBILITY OF RETURNING TO GATE BEFORE GETTING AN UPDATE FROM THE CABIN. FLT ATTENDANTS RPTED SMOKE WAS NOT CLRING. CAPT SAID WE WERE GOING TO RETURN AND TOLD ME TO COORDINATE WITH GND WHILE HE SPOKE TO FLT ATTENDANTS AND COMPANY. THERE WAS SO MUCH TFC ON GND THAT I COULD NOT GET THROUGH. AFTER SEVERAL TRIES I DIALED UP RAMP AND TOLD HIM WE NEEDED TO RETURN TO GATE AND ASKED HIM TO TELL GND. CAPT HAD A BREAK IN HIS COM AND I TOLD HIM RAMP WAS GOING TO GET GND'S ATTN. THERE WAS A BREAK AND I CALLED GND AGAIN AND HE CALLED BACK KNOWING THAT WE HAD TO RETURN AND CLRED US IN. AFTER THE TURN CAPT TALKED TO FLT ATTENDANTS AGAIN AND SMOKE WAS NOT CLRING/POSSIBLY GETTING WORSE. CAPT ASKED CFR TO MEET US AT GATE AND ASKED ME TO TELL OPS THAT PAX WOULD BE OFFLOADING RIGHT AWAY. AFTER DOORS OPEN AT GATE (L1 AND REAR STAIR/CABIN DOOR) CABIN SMOKE DISSIPATED RAPIDLY AND PAX DEPLANED WITHOUT ANY TROUBLE.