SAN FRANCISCO (CBS SF) — The Bay Area Air Quality Management District has extended the ongoing Spare the Air alert through this Friday because of smoke that continues to cover the region from various wildfires.

On Spare the Air days, the burning of wood, manufactured fire logs or other solid fuel is banned both indoors and outdoors.

The alerts are issued when smog or particulate matter pollution is expected to reach unhealthy levels in the Bay Area. The air district recommends that people stay inside with doors and windows closed until smoke levels subside.

The region has been under an alert since last Tuesday due to wildfire smoke from the lightning-sparked fires started on August 16.

As of Tuesday, the SCU Lightning Complex fires in the East and South Bay and the LNU Lightning Complex fires in the North Bay are now the second- and third-largest fires in California’s history. The CZU Lightning Complex fires burning in San Mateo and Santa Cruz counties, the Woodward Fire burning on the Point Reyes National Seashore in Marin County and multiple wildfires burning in Monterey County are also contributing to the smoke in the region.

The following online resources are available to check current air quality where you live and find out when it’s healthy to resume normal activities outside.