A wildfire burning 200 miles away can still foul the air in Mill Valley.

That's the central message of new smoke preparedness guidance published Tuesday, Aug. 11, by Fire Safe Marin, arriving as the Timber Fire near Big Sur grew to nearly 2,500 acres with just 5% containment as of Tuesday afternoon and smoke drifted into the Bay Area.

The guidance, written by Fire Safe Marin contributor Julian Kaelon, lays out concrete steps Southern Marin residents can take before, during and after smoky conditions reach the county. Kaelon wrote that smoke from the Woodside Fire in Sonoma County reached Marin in late July, followed days later by haze from wildfires in Oregon and Washington, underscoring how quickly conditions can change regardless of where a fire is burning.

Set up a clean-air room

Fire Safe Marin recommends choosing a room with the fewest windows and doors and running an air purifier there when smoke arrives. Residents should close all windows and doors, set heating or cooling systems to recirculate and avoid activities that add particles indoors: smoking, burning candles, frying food or vacuuming without a HEPA filter.

If going outside is unavoidable, wear a well-fitting N95 mask. While driving, keep windows closed and set the car's ventilation to recirculate.

Sign up for AlertMarin alerts

AlertMarin, Marin County's emergency notification system, sends urgent information by phone, text or email during wildfires and evacuations. Fire Safe Marin urges residents to sign up at emergency.marincounty.gov/sign-alertmarin, keep contact information current and allow alerts to bypass "Do Not Disturb" settings on their phones.

One lesser-known tip: when signing up, select the "Prescribed Burns" alert group. That way, when planned burns produce temporary smoke in Marin, residents will know it's controlled rather than an emergency.

Know who's most at risk

Wildfire smoke can cause coughing, headaches, irritated eyes, sore throat and trouble breathing. Children, older adults, pregnant people and those with heart or lung conditions are especially sensitive. Fire Safe Marin recommends checking real-time air quality at fire.airnow.gov before deciding whether to limit outdoor activities.

What parents should ask their schools

In a companion back-to-school guide also published Tuesday, Aug. 11, Fire Safe Marin warned parents against rushing to school during a wildfire emergency. Roads may be congested with evacuating residents and emergency vehicles, and law enforcement may block entry to evacuation zones.

Schools may respond by sheltering students in place, evacuating to another location, dismissing early or conducting controlled reunification. Fire Safe Marin recommends parents ask their district in advance how emergency updates will be sent, where students would go if the school evacuates and who is authorized to pick up their child.

Why now

As we reported Aug. 3, the Woodside Fire haze prompted a county smoke advisory for Southern Marin. Now the Timber Fire is active. The Bay Area Air Quality Management District issued an advisory for Tuesday and Wednesday, Aug. 11–12, warning that smoke could impact portions of the South Bay and East Bay. The advisory did not specifically name the North Bay, but conditions can shift rapidly.

Have a backup plan: know where you could go if your home becomes too hot, loses power or cannot keep smoke out. Once the air clears, open windows, replace dirty filters and wipe hard surfaces with soap and water to remove residue.