Improve Indoor Air Quality During Wildfires

To improve indoor air quality during wildfires, create a “clean-air room” in your home, use a portable air cleaner with a HEPA filter, and reduce the amount of outdoor smoke that gets inside. These steps help lower your exposure to fine particulate matter from wildfire smoke, the main health concern during smoke events. Keep windows and doors closed, set your HVAC system to recirculate, and avoid activities that add indoor pollutants. You don’t need to overhaul your whole house—focusing on one room where you spend most of your time is an effective and manageable approach.

Why Wildfire Smoke Is a Health Concern

Wildfire smoke contains a mix of gases and fine particles. The smallest particles, called fine particulate matter (PM2.5), are tiny enough to get deep into your lungs and even enter your bloodstream. Exposure can cause coughing, shortness of breath, irritated eyes, and worsen chronic heart and lung conditions. Children, older adults, pregnant women, and people with asthma or heart disease are more sensitive. Even if you are healthy, it is wise to reduce exposure when outdoor air quality is poor.

Create a Clean-Air Room

A clean-air room is one room in your home where you focus your efforts to keep the air as clean as possible. Choose a room you use often, such as a bedroom or living room. Ideally, it should be large enough for your household to gather, but small enough to be effectively filtered. Here’s how to set it up:

1. Close all windows and doors in the room to keep smoke out.
2. Run a portable air cleaner with a HEPA filter that is appropriately sized for the room. Run it on the highest setting you can tolerate (noise-wise) while you are in the room, and leave it running on a lower setting when you are away.
3. Set your central HVAC system to “fan on” to continuously circulate air through its filter, and close the fresh-air intake if you have one. Use the highest-efficiency filter your system can handle (MERV 13 or higher if possible).
4. Avoid adding indoor pollution in the clean-air room: no smoking, no burning candles or incense, no frying foods, and no vacuuming unless your vacuum has a HEPA filter.

If your home does not have an HVAC system, a well-sized portable air cleaner alone can make a big difference. Cover gaps under doors with a rolled towel to further reduce smoke entry.

Choose a Portable Air Cleaner

Portable air cleaners are the most effective way to filter fine particulate matter indoors. Look for a model with a true HEPA filter, which removes at least 99.97% of particles 0.3 microns in size. Avoid devices that generate ozone, such as some ionic air purifiers, as ozone itself is a respiratory irritant.

Sizing: Check the manufacturer’s recommended room size. The Clean Air Delivery Rate (CADR) for smoke should be at least two-thirds of the room’s square footage. For example, a 150 sq ft room needs a smoke CADR of at least 100. If you cannot get a properly sized unit, a smaller one run continuously still helps, especially if you stay close to it.

Budget options: If buying a portable air cleaner is not possible, you can make a DIY air cleaner using a box fan and a high-efficiency furnace filter (MERV 13 or higher). Attach the filter to the back of the fan with tape or bungee cords, making sure air flows through the filter. This is a lower-cost alternative that can significantly reduce particles in a room. Always follow safety precautions: never leave a DIY fan-filter setup unattended, and check that the fan does not overheat.

Reduce Smoke Coming Indoors

Keeping smoke out is the first line of defense. Here are practical steps:

• Keep windows and doors closed as much as possible, even when it is hot. Use fans or air conditioning (if you have it) to stay cool, but set the AC to recirculate mode so it does not pull in outdoor air.
• Check your HVAC system: If you have a central system with a fresh-air intake, close it or set the system to recirculate. Replace the filter with a high-efficiency one (MERV 13 or higher) if possible, and run the fan continuously to filter indoor air.
• Seal obvious gaps: Place damp towels under exterior doors and windows that leak. Use weatherstripping or caulk for a more permanent fix.
• Avoid using exhaust fans that vent outside, such as bathroom or kitchen fans, as they can create negative pressure and pull smoke indoors. If you must cook, use the stove hood only if it recirculates air (not vented outside) or avoid cooking that produces smoke.
• Limit opening exterior doors. If you have to go out, use one door and close it quickly behind you.

Monitor Outdoor Air Quality

Check your local air quality index (AQI) to know when to take action. The AQI is a scale from 0 to 500; higher numbers mean worse air quality. When the AQI for PM2.5 is above 100, sensitive groups should reduce exposure. Above 150, everyone should take precautions. Many weather apps and websites provide real-time AQI. You can also look for visible haze or smell smoke as a clue, but AQI is more reliable.

Adapt to Your Situation

Hot weather: Keeping windows closed can make your home hot. If you have air conditioning, use it in recirculate mode. If not, consider spending time in public buildings with filtered air, such as libraries or shopping malls, during the hottest part of the day. At home, use blinds or curtains to block sunlight and avoid using heat-generating appliances.

No air conditioning: Use fans to stay cool, but be aware that fans do not filter air. You can place a portable air cleaner near you. Stay hydrated and take cool showers.

Multiple people or large homes: Focus on one or two clean-air rooms rather than trying to clean the whole house. Ensure everyone knows which room is the designated clean room.

Low budget: DIY fan-filter setups are a viable option. Also, upgrading your HVAC filter to a higher MERV rating is relatively inexpensive and helps even if you don’t have portable cleaners.

When to Evacuate or Seek Shelter

If your indoor air quality becomes unhealthy despite your efforts, or if you experience symptoms like difficulty breathing, chest pain, or severe coughing, consider leaving the area. Public clean-air shelters may be opened during severe wildfire events. Check local news and emergency alerts for information.

Summary of Key Actions

Action	Why It Helps	Effort/Cost
Close windows and doors	Reduces smoke entry	Low / Free
Run a portable air cleaner with HEPA	Removes fine particles indoors	Medium initial cost, low ongoing
Set HVAC to recirculate and upgrade filter	Filters indoor air without pulling in smoke	Low / Filter cost
Create a DIY fan-filter	Affordable alternative to commercial cleaners	Low / about $40–$60
Avoid indoor pollution (candles, frying)	Keeps indoor air cleaner	Low / Free
Monitor AQI	Helps you know when to take action	Low / Free

By taking these steps, you can significantly improve your indoor air quality during wildfires and protect your health without turning it into a major project. Start with the clean-air room, use the air cleaning options that fit your budget and home, and adjust as conditions change.