Indoor and Outdoor Volatile Organic Compound Levels During and After the 2025 Los Angeles Wildfires

The January 2025 Los Angeles urban wildfires caused extensive destruction and exposed millions to wildfire smoke containing hazardous volatile organic compounds (VOCs). To evaluate exposure risks, we conducted indoor and outdoor VOC sampling at 24 locations during three phases: active burning, smoldering, and off-gassing. Outdoor benzene concentrations peaked during active burning but remained below OEHHA health thresholds. In contrast, indoor BTEX concentrations increased during smoldering and remained elevated during the off-gassing phase, particularly in uninhabited homes inside burn zones, suggesting persistent emissions from smoke-impacted materials. These findings raise concerns about indoor air quality post-wildfire and the potential for prolonged exposure. We recommend ventilating homes and using HEPA and activated charcoal air purifiers before reoccupying fire-affected residences. Our results highlight the need for targeted mitigation and ongoing monitoring to protect public health during wildfire recovery.