(03-26) 04:00 PDT RICHMOND -- Here is a look at some incidents at Chevron's Richmond refinery during the past decade.

* APRIL 13, 1997: A leak in a hydroprocessing plant released hydrocarbons and sour gas into the atmosphere. About 500 residents were told to remain indoors until the vapors dissipated.

* MARCH 27, 1996: A power failure caused a flare-up, which is a safety procedure to burn compounds and reduce output of toxic materials into the air. There was no apparent danger to Richmond residents.

* APRIL 13, 1994: A San Francisco man was seriously injured in a fire that began when a pump ignited in the Chevron solvent de-asphalting unit. The nonchemical and nontoxic fire was extinguished.

* JUNE 23, 1992: A yellow cloud of smoke formed when hydrocarbons escaped from a processing unit during a system shutdown. Chevron officials said the cloud created no public-health threats.

* FEB. 22, 1992: A flange leak was blamed for a fire that broke out in a gas-processing unit. The fire was quickly put out by the refinery's fire brigade and the Richmond Fire Department. Chevron officials reported no injuries.

* DEC. 19, 1991: An abnormal flare activity caused the release of the foul-smelling sulfur dioxide over Point Richmond, a residential area.

* DEC. 5, 1991: An explosion released 40 tons of catalyst dust containing nickel, vanadium, antimony and other toxins over a 16-square-mile area of Richmond.

* OCT. 30, 1991: Two injuries were suffered during a smoky fire that Chevron officials said may have been sparked by a pump failure in an oil-processing unit.

* NOV. 11, 1990: A mechanical fitting broke, and hydrogen sulfide was released into the air. No injuries were reported.

* JUNE 1, 1989: Two workers were injured after they were burned in a flash fire that erupted in the plant's wax-blending section.