The Environmental Protection Agency's air-pollution monitoring program conducted inadequate inspections about 40 percent of the time in fiscal 1984, a congressional study says.

The charges were made in a General Accounting Office report released by House Energy and Commerce Committee Chairman John D. Dingell (D-Mich.), who urged EPA Administrator Lee Thomas to "reevaluate EPA's entire inspection program."

GAO, the investigative wing of Congress, said that in fiscal 1984, state and local inspectors checked 95 percent of the 29,886 factories and buildings assigned to them under the Clean Air Act.

But the GAO report said that in 43 percent of the cases, inspections carried out under EPA guidelines were not performed often enough or in sufficient depth to ensure that a facility was complying with the law's emission standards.

GAO said the record was even worse for possible air pollution sources that were the direct responsibility of EPA's inspectors.

"EPA inspected only 539 of the 2,017 sources 27 percent it should have, citing several reasons, including lack of staff," the report said.

Other GAO findings included:

*5,916 facilities were not inspected often enough.

*969 were inspected too frequently, including seven visits to one "without any potential process or control equipment problems."

*Half of the state and local agencies responding to the GAO survey said their inspectors spent 30 percent or less of their time checking the facilities assigned to them by EPA.

*EPA funds for training their inspectors declined from $998,000 in 1981 to zero in 1985.

"According to EPA, the quality of its training courses is likely to decline and those retained will not be updated," GAO said.