WASHINGTON - Preparing information for lab tests, cleanup crews

yesterday explored the interior of the Senate office building where toxic gas was spread to kill anthrax spores.

Associated Press

With the Hart Senate Office Building in the background, William Flynn of Biomarine Inc., right foreground, leads environmental workers on Capitol Hill on Thursday in preparation to clean the building. Workers will install chemically resistant pipe and barriers to begin fumigating the building that has been closed for six weeks due to a letter tainted with deadly anthrax spores that turned up in the building.

The first team of workers entered the Hart Senate Office Building in the morning to measure chlorine dioxide gas levels and "just to see what things look like," said Richard Rupert, onsite coordinator for the Environmental Protection Agency.

Equipped with biohazard suits and air tanks, they took photographs and videotapes, checked readings and disconnected some equipment.

The gas was piped into Senate Majority Leader Tom Daschle's office suite for eight hours Saturday. After the fumigation, a second chemical, sodium bisulfite was inserted to break down the gas.

The next phase, which involved the gathering of wipe samples and test strips, was expected to last until today. Lab results from those samples were not

expected for about a week.

Early readings put the level of chlorine dioxide inside at about 800 parts per million, but it had quickly dropped to below 20 parts per million early yesterday morning, Rupert said. The goal is to eliminate all traces inside.

Outside the building, a $1 million EPA bus outfitted with sensitive monitoring equipment detected only faint traces of the gas escaping, far below the 25 parts per billion exposure acceptable to District of Columbia health officials, the EPA said.

"It went real well, and everyone's in good spirits," Rupert said of the overall operation, intended to make it possible to reopen the shuttered building where 50 senators have offices.

Daschle, D-S.D., also said the operation went smoothly.

"The monitoring would indicate, at least so far, that everything that we had expected would happen has happened," he said on NBC's "Meet the Press."

It was the first anthrax decontamination in the United States using chlorine dioxide, which began pumping into the building early Saturday.

Anthrax bacteria escaped Oct. 15 when a Daschle aide opened an anthrax-tainted letter. The senator's suite was sealed off with duct tape, plastic sheets and plywood with foam.

The rest of the office building was not similarly sealed, although the adjacent Dirksen Senate Office Building, connected by hallways with Hart, and the Hart underground garage were closed as a precaution.

Capitol Police spokesman Lt. Dan Nichols said the Dirksen building would reopen today. It was unclear whether the Hart garage also would open.