21.   Environmental Protection Agency officials were hoping that experts would approve using chlorine dioxide in the next day or two.

22.   Following repeated delays, the building was declared safe last week after several attempts to decontaminate it with chlorine dioxide, a toxic gas.

23.   Some liquid chlorine dioxide was used in the suite beforehand.

24.   The strips contain bacteria more resistant to the chlorine dioxide.

25.   These include flushing tanks and pipes with a solution of chlorine dioxide, which must remain in contact with all parts of the system for at least four hours.

26.   To test the effectiveness of the gas, technicians leave in the building strips that contain a bacteria more resistant to the chlorine dioxide than this strain of anthrax.