In March, Valero's Benicial refinery spit out pollution which caused city officials to warn residents to stay indoors. The Bay Area Air Quality Monitoring District sent a van to monitor the situation because currently there is no stationary air quality monitoring device in the residential areas despite the fact that it's home to one of the largest refineries in California. 

As explained in the article "Valer's March Pollution Release Exposes Weaknesses in Benicia's Air Monitoring System" by Ted Goldberg: 

An article by Ted Goldberg of KQED News has looked into the release of a large unexpected plume of petroleum coke dust by Valero's Benicia refinery. The release had local fire officials encouraging people with respiratory problems to avoid activity outdoors. 

A partial shutdown of the facility resulted from this incident. This is considered the worst breakdown since a 2017 power outage.

Anthony Wexler explores what is causing such poor levels of air quality, why short-term solutions aren’t working, and what we can do to mitigate these scenarios.