Some machines at the plant lacked equipment to draw the toxic dust away from workers, while other machines had equipment that worked poorly, said Mark Van Ert, an industrial hygienist.

Plant air samples over the years showed dust levels exceeded federal safety standard thousands of times, and the problems were not corrected, Van Ert said.

"My opinion is they knew they needed to control these exceedences," he said.

Van Ert testified for Brush Wellman, an Ohio-based company that supplied Rocky Flats with beryllium. His assessment of how Rocky Flats was operated came as part of the company's defense against the lawsuit, which blames Brush for the workers' lung disease caused by the metal.

Four Rocky Flats workers and their wives claim the company covered up information about how toxic the metal's dust was and never informed Rocky Flats managers that the federal safety standard for beryllium exposure failed to protect workers.

Brush blames the workers' sickness on government contractors such as Rockwell International and Dow Chemical Co. for running a shoddy safety program at the plant.

Brush also argues there was information available publicly that the federal safety standard didn't protect all workers.

Van Ert also said the plant's industrial hygienist believed the federal standard failed to protect all workers from the lung disease and that he knew that as early as 1961. The hygienist is expected to testify later.