Wildfire smoke can creep into Bay Area homes even when your windows are shut. If you have kids, older relatives, or anyone with asthma in the household, even a short smoke episode can make the air indoors feel harsh. The good news: a simple plan that combines air sealing with the right filtration can keep your indoor air cleaner and your home more comfortable during smoke season. Below, you’ll get practical steps, local programs, and sizing tips you can use right away. Let’s dive in.
Why smoke readiness matters
Bay Area smoke and your indoor air
Wildfire smoke carries fine particles called PM2.5 that can travel far and affect breathing and heart health. Public health guidance calls PM2.5 the main indoor risk during smoke events, so your goal is to keep these particles out and filter what gets in. You can learn more about health impacts from the EPA’s overview of wildfires and indoor air quality.
When to shelter vs evacuate
Staying indoors with sealed windows and filtered air is often the safest choice when air quality is unhealthy. If a fire threatens your structure, follow emergency orders and evacuate. The EPA’s guide to creating a clean room during wildfire smoke explains when to shelter and how to set up a cleaner air space.
Air sealing basics
What to seal first
Air sealing is closing the gaps that let outdoor air seep in. Focus on attic penetrations, recessed lights, rim joists, window and door perimeters, and plumbing or electrical penetrations. Duct sealing also matters, because leaky ducts can pull smoky air into living spaces.
How tightness is measured
Pros use blower-door testing to measure whole-house leakage at a set pressure called ACH50. A lower ACH50 number means a tighter envelope and usually less smoke infiltration. Learn the basics of blower doors and ACH50 from this plain-language overview.
Why sealing helps with smoke
Cutting down on uncontrolled leaks reduces how fast outdoor smoke enters your home. Studies show that homes with good air sealing paired with effective filtration see much lower indoor-to-outdoor PM2.5 ratios. A recent analysis highlights the combined benefit of sealing plus filtration for meaningful reductions in indoor smoke levels (research summary).
Balance fresh air and IAQ
A tighter home needs a plan for ventilation during normal days to maintain healthy indoor air. During heavy smoke, you should minimize outdoor intake and rely on filtration, then restore controlled ventilation after the event. Energy code and IAQ resources discuss how to balance ventilation and filtration to meet indoor air goals (technical guidance).
Bay Area incentives and help
For income-qualified households, BayREN’s EASE Home program offers weatherization help that can include air sealing and duct work. Check current offerings and eligibility on the BayREN EASE Home page. BayREN also links to other income-qualified options that may stack with state or utility programs; see the BayREN income-qualified programs overview for updates.
Filtration that works
Whole-home HVAC filters (MERV-13)
If your forced-air system can handle it, upgrade to a MERV-13 filter and run the fan on ON during smoke events so air keeps circulating through the filter. This can significantly reduce PM2.5 throughout the home. The EPA’s clean room guidance also covers HVAC settings, including setting systems to recirculate during smoke (clean room guidance).
Portable cleaners and CADR
Portable air cleaners are essential for bedrooms and main living areas. Size them by CADR so you get enough clean-air flow for each room. EPA and AHAM suggest choosing a smoke CADR roughly two-thirds of the room’s square footage, and running units on high during smoke events; see the EPA’s portable cleaner sizing tips.
DIY options that work
A well-built Corsi-Rosenthal box or a single-filter box fan unit can deliver high CADR at low cost. Use a modern, UL-listed 20-inch box fan and MERV-13 filters, and follow safety guidance. The EPA recognizes DIY units as practical temporary alternatives when commercial HEPA units are not available (DIY and clean room guidance).
Operation tips during smoke
- Close windows and doors and set HVAC to recirculate.
- Run the central fan on ON and keep portable units on high in key rooms.
- Replace HVAC and portable filters more often, because smoke loads clog filters quickly.
- Choose non-ozone producing air cleaners.
Bay Area smoke-season checklist
- Seal obvious leaks: weatherstrip doors, caulk window gaps, and seal attic access and utility penetrations. If you may qualify, check BayREN EASE Home for weatherization help.
- Upgrade filtration: if your blower can handle it, install MERV-13 and run the fan on ON during smoke. If your system cannot, use portable HEPA units in occupied rooms.
- Size portable cleaners: pick units with enough smoke CADR for bedrooms and main living areas, and keep spare filters on hand (EPA CADR guidance).
- Know local alerts: sign up for BAAQMD’s Spare the Air and incident notifications so you can act fast during smoke days (BAAQMD guidance and alerts).
- Plan for smoke and heat: if cooling or power limits make it unsafe to stay home, identify clean-air centers and consider relocation until conditions improve (EPA preparedness).
Set expectations and tradeoffs
Air sealing alone will not keep all smoke out. You get the biggest benefit when you pair sealing with MERV-13 or HEPA filtration and run your HVAC fan for constant circulation. Be aware that some older HVAC systems cannot handle a MERV-13 filter without a blower or duct upgrade; in that case, prioritize portable HEPA or DIY units in critical rooms (evidence summary).
Make a clean air plan now
You do not need a full remodel to make a big difference. A weekend of sealing priority gaps, a MERV-13 upgrade if your system allows it, and correctly sized portable cleaners can transform your indoor air during smoke events. If you are weighing repairs versus selling a property as-is, or you want to position an investment property for the next smoke season, connect with Acquire'd Real Estate for straightforward options.
FAQs
Will air sealing keep all wildfire smoke out of my Bay Area home?
- No. Sealing lowers infiltration but does not make a home airtight. Combining sealing with MERV-13 or HEPA filtration and running the HVAC fan on ON yields much larger PM2.5 reductions (supporting research).
During heavy smoke, should I bring in outside air or recirculate?
- Recirculate. Close windows and doors, set systems to recirculate, and run filtration. Restore normal ventilation after the smoke event (EPA clean room guidance).
How do I size a portable air cleaner for a bedroom or living room?
- Use CADR. Choose a smoke CADR roughly two-thirds of the room’s square footage and run the unit on high during smoke episodes (EPA sizing tips).
Are DIY Corsi-Rosenthal boxes safe and effective for wildfire smoke?
- Yes, when built correctly with a modern UL-listed box fan and MERV-13 filters. They are effective, low-cost, and intended as temporary alternatives to commercial HEPA units (EPA DIY guidance).
Where can I find Bay Area alerts and local smoke guidance?
- Sign up for BAAQMD Spare the Air alerts and review current smoke preparedness tips for residents (BAAQMD alerts and guidance).
