A firearms specialist and his wife were injured early yesterday morning when a combination of firearms, gunpowder and solvents blew off the end of their suburban home in Woodbridge.

Fire officials said they were amazed that the damage wasn't more severe.

Investigators said they discovered "an arsenal" of 119 firearms and other explosive materials in the home occupied by Richard (Hook) Taylor, 52, a retired D. C. police officer and currently a firearms instructor for the U.S. Drug Enforcement Administration.

"Those people sure were lucky," said James Mastin, deputy fire marshal for Prince William County. "Why, [Traylor] had enough stuff down there to knock the whole block off."

As it was, the two explosions and a flash fire that followed appeared to have done relatively light damage to the Traylor's four-bedroom house at 1713 Azalea Lane, where an entire 24-foot wall was knocked out by the explosion. Furniture in the rooms along the wall was left standing and appeared undamaged.

Traylor, who was described as a gun collector who liked to prepare his own ammunition, suffered second-degree burns over 30 percent of his body. He was flown by helicopter to Washington Hospital Center and was listed there last night in serious but stable condition. His wife, Patricia, 49, was treated at Potomac Hospital in Woodbridge for an ear injury and released. A son, William, 22, and daughter, Leza, 18, who were in the house at the time were not injured.

"W know what exploded, just not why," said deputy fire marshal Mastin. The explosion was being investigated by the FBI and the Bureau of Alcohol, Tobacco and Firearms, as well as Mastin's office.

After firemen quickly extinguished a flash fire at the house, they found several cans of gunpowder stored in metal cabinets near the center of the explosion, Mastin said. "It was really a wonder they didn't go off," he said. "They really shouldn't allow an arsenal like that in a residential neighborhood."

Fire officials said the presence of the materials did not violate any local or Virginia laws.

John Rawley, a special agent in charge of the ATF Falls Church bureau, said agents found 119 firearms and a "large quantity" of ammunition in the home.

Fire officials said the incident began when Traylor and his wife were awakened by a small explosion at 4:11 a.m. When Traylor went to investigate, a second explosion threw him back into the bedroom and blew off the side of the two-story house.

"It sounded like a thunderstrom at first," said Leza, who was asleep at the time of the explosion.

Lauren and Valerie Page, who live across the street from the Traylors' residence, said they heard shots "popping like popcorn" after the second explosion hit the usually quiet residential neighborhood near the Occoquan River.

Traylor, regarded as an expert marksman by his fellow officers, retired last summer from the Metropolitan Police Department after 23 years on the force. He had been head of the department's award-winning pistol team that had competed in shooting matches across the United States.

Three D.C. policemen drove to Traylor's home yesterday with a load of lumber to shore up the side of the house, which sat open like a doll house, exposing a slightly charred chest of drawers in the bedroom where the Traylors slept.

A friend who watched as agents scoured the area around the home, said he had worked with the injured man on the pistol range at Lorton, where Traylor trained the D.C. civil disturbance unit in firearms. "He's one of the best, he'd know how to properly care for it." CAPTION: Picture 1, Fireman inspect damage to Woodbridge home where a predawn explosion knocked off one wall of the house. by Larry Morris-The Washington Post; Picture 2, A Bureau of Alcohol, Tobacco and Firearms investigator photographs explosion damage to Woodbridge home.