A huge plume of black smoke belched into the sky from the Chevron refinery in Richmond, California on Tuesday, the second such incident at a Chevron refinery in the state in three days. The refinery blamed an “unplanned” release of “an unknown amount of SO2 [sulfur dioxide] … causing smoke to come out from the flares.” Chevron insisted the cloud of black smoke posed no threat to public health. “This is Chevron’s 13th flaring incident of the year. That is more than the number of flaring operations conducted by all other Bay Area refineries combined so far in 2021,” KQED senior editor Ted Goldberg wrote on Twitter. The incident comes just days after flaring at another Chevron refinery in El Segundo, California, lit up the night sky and produced smoke plumes visible for miles. (Richmond: (ABC-7 KGO News, SFGate, NBC Bay Area, KTVU; El Segundo refinery: LA Times $)