CONCORD -- The Tesoro Refinery in North Concord experienced a power outage Friday afternoon and burned off the flammable gas that built up during the outage, county officials.

The burn off caused a thin layer of black smoke above the facility, according to Steve Morioka, assistant director with Contra Costa Health Services Hazardous Material Program. It was not known how long the smoke would remain in the area.

The outage took place about 11:29 a.m., according to Mike Marcy, director of external affairs for the refinery. As a safety precaution, workers shut down processing units, then vented the excess hydrocarbon vapors by pipeline to flares.

Power was back up by about 11:47 a.m., Marcy said. He added that the refinery's ground-level monitors did not detect any emissions around the property.

Following the outage, a public health advisory for Martinez, Pacheco, North Concord and Clyde was issued.

Health officials warned that although most people will not be affected, the smoke could affect individuals with respiratory sensitivities. Eye, skin, nose or throat irritation may be possible for some people in the area.

Anyone who experiences irritation is advised to rinse any irritated area of the body with water.

For more information visit www.cococws.us.

Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.