Characterizing Indoor Surface VOC Contamination after the 2025 Los Angeles Fires

We quantify volatile organic compound (VOC) emissions from indoor surface swabs and portable air cleaner (PAC) filters collected in a home 30 days after the 2025 Los Angeles wildland-urban interface (WUI) fires. We calculate emissions for 17 fire-relevant compounds. Surface emissions exceeded those of clean controls, and emissions from a windowsill in a room without a PAC were ∼15× and ∼2× higher for benzene and toluene, respectively, than rates reported in the literature for comparable materials unaffected by smoke/soot. Particle filters installed in PACs at the start of the fire emitted aromatics at rates comparable to those reported in a study where filters operated for 200 days in a city. Emissions from activated carbon filters exceeded those of the particle filters tested as part of the present study by >3×. A windowsill in a room without a PAC off-gassed more VOC mass than a windowsill in a room with a PAC, suggesting that air cleaners can reduce surface contamination. Modeling with benzene emission rates from impacted surfaces in a hypothetical indoor space resulted in a predicted indoor concentration ∼6× greater than outdoors. This study shows surfaces act as persistent VOC sources following WUI fires and indicates indoor surfaces affect exposure during and after fire events.