Despite a thick cloud of smoke covering a good portion of western Contra Costa County from a fire at the Chevron refinery in Richmond on Monday night, the air quality was minimally impacted, according to the Bay Area Air Quality Management District.
The air district inspectors collected samples of the air and tested them in the district's lab, finding pollution levels well below the federal health standards, the air district said in a statement.
"Surface winds were light and heat pushed the smoke upwards where stronger winds helped disperse it," the statement said.
The Contra Costa County Health Services tests to track hydrogen sulfate and volatile organic compounds both came up negative, said a health services spokeswoman.
Air samples were taken by health services officials, but test results were not available as of 5 p.m., she said.
The three-alarm fire broke out at 4 Crude Unit at about 6:30 p.m. and was burning strong before it was contained just before 11 p.m.
More than 500 people - more than 300 at Doctors Medical Center in San Pablo and 200-plus at Kaiser Permanente in Richmond - were treated for respiratory issues.