Chevron oil refinery fire in US

Smoke pours from a fire at the Chevron Richmond Refinery, seen behind Alcatraz Island in San Francisco, Monday, Aug. 6, 2012. Officials have told residents of two Northern California cities to shelter in place as a fire at the refinery releases plumes of black smoke.(AP Photo/Eric Risberg)

Firefighting crews continue to pour water onto a unit after a fire at a Chevron refinery on Tuesday, Aug. 7, 2012 in Richmond, Calif. The fire, which sent plumes of black smoke over the San Francisco Bay area, erupted Monday evening in the massive Chevron refinery about 10 miles (16 kilometers) northeast of San Francisco. It was out early Tuesday. (AP Photo/The Contra Costa Times, Aric Crabb)

Firefighting crews continue to pour water onto a unit after a fire at a Chevron refinery on Tuesday, Aug. 7, 2012 in Richmond, Calif. The fire, which sent plumes of black smoke over the San Francisco Bay area, erupted Monday evening in the massive Chevron refinery about 10 miles (16 kilometers) northeast of San Francisco. It was out early Tuesday. (AP Photo/The Contra Costa Times, Aric Crabb)

Firefighting crews continue to pour water onto a unit after a fire at a Chevron refinery on Tuesday, Aug. 7, 2012 in Richmond, Calif. The fire, which sent plumes of black smoke over the San Francisco Bay area, erupted Monday evening in the massive Chevron refinery about 10 miles (16 kilometers) northeast of San Francisco. It was out early Tuesday. (AP Photo/The Contra Costa Times, Aric Crabb)

A man pumps gas at a Chevron gas station in San Francisco, Tuesday, Aug. 7, 2012. A major fire at one of the country's biggest oil refineries will help trigger a rise in oil and gas prices in California and elsewhere on the West Coast, analysts say. (AP Photo/Jeff Chiu)

Smoke and flame billow from a crude oil unit at the Chevron refinery in Richmond, Calif., Monday, Aug. 6, 2012. The facility makes high quality products that include gasoline, jet fuel, diesel fuel and lubricants, as well as chemicals used to manufacture many other useful products. (AP Photo/The Contra Costa Times, D. Ross Cameron )

Smoke pours from a fire at the Chevron Richmond Refinery, seen at left behind Alcatraz Island as a catamaran sails by in San Francisco, Monday, Aug. 6, 2012. Officials have told residents of two Northern California cities to shelter in place as the fire in Richmond releases plumes of black smoke. The fire, first reported at 6 40 p.m. Monday, is burning in a process unit at the refinery, officials said. (AP Photo/Eric Risberg)