In the first action of its kind, the California Air Resources Board has certified equipment enabling four types of Ford truck engines to operate on compressed natural gas and meet the state's stringent vehicle-emission standards.

The fuel-equipment manufacturer, GFI Control Systems, Inc. of Ontario, Canada, had to demonstrate that engines using the equipment could meet California emission standards after 50,000 miles of use and therefore are as clean or cleaner than conventional gasoline engines.

Previously, the Air Resources Board only required manufacturers to demonstrate that engines with alternative-fuel equipment could meet state standards at the time of the equipment's installation. Conventional gasoline engines are subject to 100,000-mile emission standards.

 "Our new practice of certifying alternative-fuel equipment for extended use improves our ability to control air pollution," Air Resources Board Chairman John D. Dunlap said. "We can feel confident that such equipment will keep vehicle emissions at acceptable levels even after the vehicle has been driven for thousands of miles."

Air Resources Board staff certified four separate "retrofit systems" manufactured by GFI Control Systems for use on 1994 and 1995 light-duty and medium-duty Ford truck engines. The equipment enables the truck engines to operate on either compressed natural gas or conventional gasoline.