A Northwest Washington office building was evacuated yesterday afternoon when a small fire in the garage ignited a sealant being spread on the floor, according to a D.C. fire department official. The department's hazardous materials unit was called in, and the 1900 block of Pennsylvania Avenue NW was closed to traffic for several hours.

Deputy Chief Joseph Herr said five men who had been working in the garage and had direct contact with smoke from the fire were decontaminated in shower stalls set up on the street. Herr said one person working in the building was sent to the hospital for reasons unrelated to the chemical fire.

In another hazardous materials incident yesterday, two people were treated for carbon monoxide poisoning after becoming ill while on a boat in Annapolis harbor, according to the Maryland Natural Resources police.

William J. Pace, of Glen Rock, Pa., and Rebecca Anne Graham, of Annapolis, were on Pace's 52-foot boat about 10 a.m. when they began to feel ill, Natural Resources police spokesman Richard McIntire said.

McIntire said officials believed carbon monoxide fumes may have seeped into the passenger compartment after an on board generator was switched on.

The two were treated at the Maryland Shock Trauma Center in Baltimore and released, a hospital spokeswoman said. After the incident in Washington, Lisa Saisselin, a spokeswoman for George Washington University Hospital, said five men were brought to the hospital from the scene. One was being examined after having been decontaminated and the other four had "health considerations," she said.

Herr said the sealant apparently contained one or more forms of alcohol and on a scale of zero to four, it had a flammable rating of three.

"They had the concrete sealant in three 55-gallon drums," Herr said as he stood outside the building. "They were working in a 200-by-200-foot area when an electrical extension cord shorted and caused a flash fire. They contained the fire and called us, and we evacuated the building."

Building employees and firefighters went floor to floor warning people to leave. The building houses mostly law offices. Among those who were at work yesterday were lawyer Scott Schoenfeld of Jenkins & Gilchrist and his secretary, Gladys Colon-Flowers.

"When they told us to leave the building, we carried our work out here," Schoenfeld said. "I have a court deadline on Monday and I couldn't afford to give up two to three hours of work."

Schoenfeld and Colon-Flowers sat on a low wall across the street from their office building and continued working on the case.

Later they stood in line waiting to have their vital signs checked along with Colon-Flowers's three children, who had come to work with her. Right behind them was "computer guy" Steve Flanagan, who had just arrived for work when he was ushered out of the building.

"I've got to get back in there," Flanagan said at 5:30 p.m. "I'm on call this weekend and I got a bunch of work to do."

Herr said that the fire department responded to the initial call about 2:20 p.m.

CAPTION: D.C. firefighter William Joseph, center, addresses people who were inside the building behind him about decontamination procedures.

CAPTION: D.C. paramedic Derrick Boone checks the vital signs of Jarvis Clark, a porter who was in the office building when the fire broke out.