The worker who survived a 14-story plunge down an air duct in a building under construction in Tysons Corner slipped on a board covering the duct and tumbled backward, his wife said yesterday.

"It was just an accident, plain and simple," Lianetta Ruettgers said of the Tuesday morning incident. "He just happened to step on that board."

Edward Ruettgers' fall from the penthouse level above the 17th floor was broken at the fourth floor when Ruettgers became wedged in a narrow section of the air duct. Rescue workers cut through the duct to reach him and lowered him to the ground by a construction elevator on the side of the concrete and glass structure.

Ruettgers, 51, remained in serious condition yesterday in the intensive care unit at Fairfax Hospital, spokesman Lon Walls said. Ruettgers has a fractured spine and cannot move his legs, but "he's going to make it," Walls said. It is not known if the paralysis is permanent, the spokesman said.

"He's in pain, as you can imagine," Lianetta Ruettgers said yesterday from the couple's home at 9303 Victoria St. in Manassas. "But I feel, like everybody else, that it's a miracle he did survive, that he didn't fall all the way down to the floor. I appreciate everyone for their concern and . . . thoughts."

Ruettgers had been working on the addition to the First American Bank building for about a month, his wife said. The 17-story-plus-penthouse building, at 1970 Chain Bridge Rd. near Tysons Corner Center, is one of the tallest buildings in the county. It is scheduled for completion in July.

The sheet metal air duct that Ruettgers fell into runs the full height of the building. At its top, it is about 2-by-4 feet wide; it narrows to about 18-by-18 inches at the spot where Ruettgers became wedged.

The Virginia Occupational Safety and Health Program is investigating the accident, spokeswoman Jan Hathcock said.