WASHINGTON (AP) _ A third attempt at fumigating the Hart Senate Office Building with poisonous gas appears to have killed remaining anthrax spores, federal environmental officials say.
The hopeful but preliminary results of the Friday-to-Monday work still must be confirmed by laboratory results that will take several days.
``We feel very comfortable that we had a very successful fumigation,'' Richard Rupert, the Environmental Protection Agency's on-scene coordinator, said in an interview Tuesday.
``We feel that based on the humidity numbers, the temperature and the concentration of chlorine dioxide, we were able to effectively destroy any anthrax spores.''
Technicians under the environmental agency's direction began pumping chlorine dioxide gas into the heating and ventilation system of the southeast quadrant of the building at 9 a.m. Friday. The process was completed at 4:30 a.m. Monday.
The quadrant had tested positive for traces of anthrax spores after the first fumigation effort, which took place on Dec. 1. A second fumigation attempt on Dec. 16 failed when workers could not create the necessary levels of humidity for the gas to work properly.
The building, where half the 100 senators have their offices, closed Oct. 17, two days after an aide to Senate Majority Leader Tom Daschle opened an anthrax-tainted letter.
Daschle said Sunday there was a reasonable possibility the building would reopen this month.
Officials were awaiting results, possibly later this week, on two types of laboratory tests.
One analysis was under way on more than 400 Band-Aid-size strips that would provide the results of the fumigation. Separate tests were checking samples taken from swabbing and vacuuming surfaces.
The test strips contain bacteria more resistant to the gas fumigation than anthrax. If that bacteria is found dead, it will suggest any remaining anthrax is too.
The surface samples were gathered by using small vacuum cleaners that have sock-like filters that are then analyzed, as well as by swabbing surfaces with something similar to a Q-Tip. Technicians also wiped surfaces with a synthetic cloth the size of a handkerchief.
Rupert said more than 4,000 samples were taken in all _ some from every room in the Hart building, which has offices surrounding a large open space in the center.
Five people have died from anthrax since early October and 18 more were infected. Thousands of others were exposed to the spores, but with a Jan. 7 deadline approaching, officials said fewer than 100 people have opted to receive an anthrax vaccine offered as an additional therapy.
Of the more than 3,000 people who have sought counseling to help decide if they need the extra therapy, more than 700 chose to take additional antibiotics.
The CDC offered voluntary extra therapy _ either 40 days of additional antibiotics or vaccine _ to those exposed. That's because animal studies suggest that in rare cases, anthrax can lurk in the body for more than the 60 days that these people were prescribed antibiotics, erupting after the drug treatment is finished.
Four dozen Capitol Hill workers received the first vaccinations on Dec. 20. Since then, an additional 39 people, mostly postal workers, in Washington, New York, New Jersey and Florida have been vaccinated, CDC figures show. U.S. Postal Service officials counted an additional 10 inoculations.