In recent days, as California’s air pollution map shifted from healthier green and yellow to red and purple — and then dark purple — officials from Los Angeles to North California urged residents to stay indoors and wear white N95 masks when they could not avoid leaving their homes. Even in Los Angeles, where smoke from the Woolsey fire had subsided by late Thursday, the air was still hazy and many schools required children to take recess inside.

For anyone who must go outside, the state public health department recommends P100 masks and N95 respirators, both of which are approved by the National Institute for Occupational Safety and Health for use by firefighters.

But Sacramento will no longer distribute N95 masks, warning that for those not living next to the fire, their risks outweigh their benefits. Risks include increased heart rate.

In the Bay Area, the National Weather Service said smoke would linger in the region into the coming week. The unhealthy air in Berkeley forced the California and Stanford football showdown to be pushed back until Dec. 1, the first postponement of the Big Game since the rivals’ 1963 match was delayed after the assassination of President John F. Kennedy.

In the communities around Paradise, air quality is considered hazardous for everyone, and the county health department is urging people to remain inside. But this has been difficult for evacuees. More than 81,000 people have been forced from their homes and many are sleeping outside in tents, unable to find other shelter.