WASHINGTON (AP) _ The latest effort to remove residual anthrax spores from the heating and ventilation system of a Senate office building was heading into a third day late Saturday.
Capitol Police Lt. Dan Nichols said at midday that fumigation of the Hart Senate Office Building should be completed Saturday evening, but officials later decided to give the process an additional 12 hours.
Environmental Protection Agency spokeswoman Bonnie Piper said a couple of hours after nightfall Saturday that technicians hoped to finish by midmorning Sunday.
The building has been closed since Oct. 17, two days after an anthrax-laced letter was opened in the office of Senate Majority Leader Tom Daschle.
On Friday, technicians began pumping steam into the ventilation system to raise humidity. At first, as in a past attempt, the humidity remained below optimum levels.
Anthrax-killing chlorine dioxide was added at 5:30 p.m., EPA spokeswoman Jennifer Browne said. ``They've got the humidity where they need it,'' she said. ``Everything is going as expected.''
To test the effectiveness of the gas, technicians have placed strips in the building that contain a bacteria more resistant to the chlorine dioxide than this strain of anthrax, Browne said. If the gas kills those bacteria, it is a good indicator that the anthrax is dead as well.
Nichols said the fumigation work, initially expected to be finished Saturday morning, was not being rushed. ``We've decided to continue the fumigation to make sure we have a good kill of the anthrax spores,'' he said.
Piper said Saturday evening the fumigation was extended yet again because concentration levels of the gas had not remained at consistent levels during the first 24 hours.
``These are normal engineering challenges which often occur during this type of operation,'' she said. ``EPA is taking appropriate action in an effort to achieve the necessary saturation levels. The process is expected to run at least another 12 hours to make sure that the fumigation is successful.''
Two previous attempts to clean the building failed to eliminate the potentially deadly spores.
While other work was being done inside the building to remove anthrax, the EPA has said it hoped this would be the final fumigation using toxic gas.
Once the fumigation process is completed, another 72 hours of testing probably will be necessary before the building is declared safe, experts said.
Officials have refused to speculate about when the building might reopen.