Wildfires are no longer just a problem for remote forests. Increasingly, they burn in or near urban areas, consuming far more than trees. Homes, cars, plastics, paints, and other building materials release a toxic mix of substances when they ignite, including volatile organic compounds (VOCs), heavy metals like lead and arsenic, dioxins, and carcinogenic polycyclic aromatic hydrocarbons (PAHs).

These pollutants, combined with fine particulate matter (PM2.5), can travel hundreds of miles from the flames. Together, they create a dangerous cocktail that threatens respiratory, cardiovascular, and neurological health—not only for residents but also for emergency responders, schools, and businesses.

Why You Might See Ash Even When AQI Looks “Good”

The Air Quality Index (AQI) is a valuable tool, but during wildfires it doesn’t always capture the full risk. One key reason: many wildfire ash particles are larger than the PM2.5 or PM10 measurements that AQI relies on. That means ash may be visible even while official readings look “good” or “moderate.”

But “green” AQI numbers don’t guarantee safety. Ash often contains harmful compounds that irritate the eyes, throat, and lungs, aggravate asthma and heart conditions, and raise long-term health risks. Vulnerable groups—children, older adults, pregnant people, and those with respiratory or cardiovascular disease—are especially at risk.

After the Flames: Restoring Indoor Air Quality

Even after outdoor smoke clears, wildfire pollution lingers indoors. Ash, soot, and fine particles settle on surfaces, carpets, furniture, ducts, and HVAC systems. Without intervention, the air you breathe indoors may remain contaminated long after skies appear clear.

Here are key steps to restore and maintain healthy indoor air quality:

• Monitor first
  Use real-time indoor and outdoor air quality monitors to understand what’s in the air you breathe. If outdoor air is better than indoors, ventilate. If not, keeps windows and doors closed and seal gaps.

• Clean safely
  When cleaning ash or soot, wear protective gear (masks, goggles, gloves, etc.) gear. Mist surfaces with water before sweeping to prevent particles from becoming airborne. Avoid using tools like leaf blowers that stir up ash, and dispose of ash properly.

• Filter and purify
  Run high-performance air purifiers, ideally with HEPA or better filtration, in frequently used rooms. Ensure that HVAC systems have efficient filters are well-maintained.

• Reduce additional sources of pollution
  Avoid burning candles, fireplaces, or using gas stoves during or after wildfire smoke episodes. Many household products also emit VOCs—try to use non-toxic cleaners and minimize added airborne pollutants via aerosol sprays.

• Clean up and maintain
  Wash pets and toys that may have ash, launder textiles, vacuum with HEPA filters, and periodically inspect and replace filters in air purifiers and HVAC systems. Regularly cleaning surfaces reduces the accumulation of settled soot and ash.




 
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Awareness + Action = Resilience

Wildfire smoke and ash are more than temporary nuisances or inconveniences—they are invisible threats that can persist indoors and long after a fire subsides. Because AQI alone can’t always reflect every risk, communities, workplaces, and responders need to rely on monitoring, safe cleanup, and high-quality filtration to reduce exposure and protect your indoor environment. With good preparation, safe cleanup, and maintaining clean indoor air, it’s possible to reduce risk and help ensure your home remains a healthy refuge—no matter what the skies look like. 

As urban wildfires become more common in a changing climate, it is critical to integrate air quality protection into disaster preparedness and recovery planning. From homes and schools to hospitals and businesses, safeguarding indoor air is an essential step in building healthier, more resilient communities.