On April 1, 2000, approximately 2000 Pacific standard time, a McDonnell Douglas MD-82, N934AS, registered to Wilmington Trust Company, operated by Alaska Airlines, Inc., and crewed by two airline transport pilots (captain and first officer) and three cabin attendants, was undamaged during an emergency evacuation at gate C-9 at the Seattle-Tacoma International Airport, Seattle, Washington. Visual meteorological night conditions existed and an IFR flight plan had been filed. None of the 140 passengers or crew aboard were injured during their egress and there was no fire. The flight, operating as flight 660, destined for Las Vegas, Nevada, was scheduled to depart at 1953, and was to have been operated under 14CFR121 as a regularly scheduled, domestic passenger flight. The aircraft was parked at gate C-9 with the jet ramp still connected to exit L-1 at the time of the event. The Captain's irregularity report stated that "Gnd pwr failed, cabin being ventilated with gnd tie thru rt pack. APU inop. Cabin filled with smoke, passengers deplaned fwd entry. Due to no power, aft flt attendant deployed left aft slide." One of the three flight attendants was stationed aft near row 24 and reported that the boarding of the aircraft was almost complete when the cabin lights went out and the (emergency) track lights illuminated. The flight attendant remarked to the passengers that "our ground power must have disconnected..." and shortly thereafter one passenger stated "I smell burning, don't you?" and another passenger remarked "I smell it also." The flight attendant then attempted to contact the cockpit via the interphone without success. She stated that "by this time smoke was coming into the cabin..." and she began to urge the passengers to exit the aircraft. The flight attendant stated that passengers were beginning to panic and were not moving up the center aisle. She then returned to the interphone (located near the galley area at exit L-2, refer to DIAGRAM I) and again attempted to contact the cockpit without success. After unsuccessfully trying to communicate via the aircraft public address system, the flight attendant chose to open exit L-2 and activate the emergency escape slide. Upon opening the door she realized the emergency escape slide had not been armed whereupon she re-closed the door, armed the slide, and re-opened the door resulting in the slide deploying (Note: emergency escape slides are not normally armed until after the aircraft leaves the gate as a ground safety procedure). A nearby passenger then indicated that passengers were moving up the aisle. The flight attendant began to urge everyone forward up the center aisle towards exit L-1, rather than utilizing the escape slide, so as to minimize injuries during egress. All passengers and crew left the aircraft via exit L-1 and the emergency escape slide was unused. The aircraft was subsequently checked and released for the flight to Las Vegas with the same cockpit crew and a new cabin crew. A maintenance examination disclosed no evidence of any aircraft related cause for the smoke. Additionally, maintenance personnel reported that the external air conditioning unit's intake pulled exhaust from the nearby electrical ground power cart and this air/exhaust mixture was then ducted into the aircraft cabin.