Although board members are concerned about maintenance shortcomings, they don't think drastic measures are required, said A.J. Eggenberger, the board's vice chairman. The key piece of a HEPA device is a fiberglasslike filter that's usually the thickness of a typical desk blotter. Age makes these filters brittle and water weakens them, so they need to be replaced periodically. DOE doesn't have set rules for how often the various types of HEPA filters should be checked or when they must be replaced, the defense board report said. The greatest threat involving a HEPA filter would be from a fire in a facility holding radioactive material, the report said.
Dense smoke can overload a filter with particles, eventually breaking it.
And water from firefighting efforts would further weaken a filter, the report said. Glines said Hanford currently tests all HEPA filters at least annually, and those filters must meet industrial standards to stay in place. Hanford does not have specific age limits on its many types of filters. But the site is looking into that matter, he said. Some Hanford filters are changed frequently.