After delay, fumigation of Hart building begins

WASHINGTON (CNN) -- Workers began their latest fumigation of the Hart Senate Office Building late Sunday afternoon, hoping to solve an anthrax problem House Minority Leader Richard Gephardt deemed "more serious than any of us thought."

The clean-up of the building's heating, ventilation and air-conditioning systems had been delayed two days by technical difficulties, and should be completed by 4 a.m. EST Monday, officials said.

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The building has been closed since October 17, when aides to Senate Majority Leader Tom Daschle open an anthrax-letter in his office. Several other congressional office buildings also showed evidence of anthrax contamination and had to fumigated.

Experts had been unable until Sunday to raise the humidity inside the Hart building to 75 percent, the level needed for fumigation, said Richard Rupert, who is coordinating the effort for the Environmental Protection Agency.

"We've been madly working 24 hours a day," Rupert said.

Chlorine dioxide gas will be pumped through the structure's heating, ventilation and AC systems for about nine hours, he said. Workers will spend another four hours removing the gas from the system.

A similar process had been conducted on December 1, the day after authorities had sealed off Daschle's suite. Rupert called that clean-up successful, though traces of anthrax were later detected.

"I'm told by the experts that it's going to take a long time to make sure that all the spores are out of the building, " Gephardt said Sunday. "And even when they're at that point, there'll still be the possibility of spores being left behind."

Experts "don't think that's dangerous, but this certainly has been a tougher decontamination job than anybody expected," Gephardt said.

In about a week, tests will determine whether all the anthrax has been eradicated from the Hart building, Rupert said.

The anthrax cleanup at the Longworth House Office Building has been completed, but it will take about a week to renovate the offices to make the sure the building is habitable, said Capitol Hill police said. Several offices in the Ford House Office Building also remain closed.