Fire smoke, rich in toxic ultrafine particles and polycyclic aromatic hydrocarbons (PAHs), poses significant health risks to first responders and vulnerable populations. In this study, a reproducible combustion–smoke simulation platform was developed to mechanistically quantify fire behavior, particle emissions, and PAH toxicity under controlled heat flux and oxygen conditions. Consistent combustion and smoke emissions were achieved by measuring heat release rate, particle mass, particle number concentration, and PAH concentration, with an overall average coefficient of variation below 15%. Systematic experiments with representative biomass (pine, oak) and plastics (PVC, polystyrene) demonstrate that fuel composition, heat flux, and oxygen availability jointly govern particle formation and PAH partitioning. Regardless of the combustion factors, ultrafine particles dominated the particle number concentration (55.5–86.2%). Plastic combustion generated 7 to 59 times particle mass, up to 260 times higher PAH emissions, and up to 58,500 times greater PAH toxic equivalent quotient (PAH-TEQ) than wood. Oxygen-deficient and smoldering regimes shifted emissions toward fine and ultrafine particles enriched in high-molecular-weight PAHs, revealing a coupled physical–chemical hazard not captured by bulk PM metrics alone. These results establish a quantitative framework linking combustion regime, particle size, and PAH toxicity, providing critical insight for exposure assessment, PPE design, and mitigation strategies in ventilation-limited and mixed-fuel fire scenarios.

Lithium-ion battery fires present complex aerosol hazards that vary substantially with oxygen availability; however, the effects of oxygen depletion on particulate emissions, soot transformation, and contamination pathways remain poorly characterized. Here, LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC811) 18650 cells (2.5 Ah) were tested across a 12-condition state-of-charge–oxygen matrix (0–70% SOC; 20.95%, 7%, and 0% O₂) under 50 kW/m² radiant heating. Reducing O₂ decreased peak heat release rate by 47–71% but increased total particulate matter by 22–158% and particle number concentration by 84–134%. Ultrafine particles (≤100 nm) dominated particle emissions, accounting for 80–94% of total counts. Airborne metal emissions exhibited a non-monotonic oxygen response, reaching 11.90 ± 0.68 µg/m³ at 7% O₂ and 70% SOC, representing a 65% increase relative to normoxic (20.95% O₂) conditions. Multi-technique soot characterization (HRTEM, Raman spectroscopy, and XPS) revealed increased carbon ordering under oxygen depletion, evidenced by reduced D1/G ratios (0.386→0.261), decreased fringe tortuosity (1.37→1.13), and substantially lower oxygenated surface carbon. Soot–metal aggregate particle diameters increased from 47 ± 9 to 61 ± 11 nm. SEM–EDS identified Ni- and Co-rich particle deposition throughout firefighter PPE layers under reduced or absent flaming conditions. These results demonstrate that oxygen depletion shifts NMC battery-fire emissions toward enhanced ultrafine particle loading, persistent metal-containing aerosols, and more ordered soot structures, providing source-characterization data for battery-fire hazard assessment and for future validation of mitigation, exposure-control, and PPE-contamination protocols.

Wildland-urban interface (WUI) and lithium-ion battery-involved fires are emerging hazardous emission sources that generate chemically complex smoke containing carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAHs) together with toxic metal-rich aerosols. This combined organic–metal mixture creates an unresolved exposure-assessment challenge for firefighters and fire-affected communities because low-burden passive samplers have not been evaluated for simultaneous PAH and metal capture under fire-smoke conditions. Here, six chemically and structurally distinct candidate materials: silicone wristband (SWB), polyurethane foam (PUF), activated carbon felt (ACF), thermoplastic polyurethane nanofiber (TPU), cotton fabric (CF), and cotton ball (CB) were exposed to controlled smoke from pine, pine + polystyrene (PS), and pine + battery scenarios and benchmarked against active reference sampling. Active sampling confirmed source-specific hazards: total PAHs increased from 10.2 µg m⁻³ in pine smoke to 167.8 µg m⁻³ with PS, whereas the battery scenario produced a metal-dominated aerosol, especially nickel (~840 µg m⁻³). Passive capture was strongly material-dependent. PUF retained the highest total PAH loading (~1.50 µg cm⁻²), ACF selectively enriched volatile naphthalene, and SWB retained the highest battery-derived metal loading (~46 µg cm⁻²). SEM-EDS showed that PAH and metal retention followed distinct mechanisms: sorption and phase partitioning for PAHs versus deposition and surface retention of metal-bearing particles. Therefore, no single passive material represented the full combined hazard. These findings support a complementary, multi-material passive sampling strategy for source-resolved PAH-metal hazard assessment, protective-equipment evaluation, decontamination studies, and future exposure-reduction efforts in fire-affected settings.

Combustion-derived polycyclic aromatic hydrocarbons (PAHs) are semi-volatile contaminants that remain on protective textiles after smoke exposure. In this study, a controlled laboratory method for smoke exposure was developed to assess the layer-specific accumulation and redistribution of PAHs in firefighter personal protective equipment (PPE). Multilayer assemblies comprising an outer shell (OS), a moisture barrier (MB), and a thermal liner (TL) were exposed to pine/polystyrene smoke generated in an atmosphere-controlled combustion chamber (50 kW m-2 heat flux, 20.95% O2, 35 min). Particle mass emissions were measured, soot-like deposits characterized by SEM and GC-MS were used to quantify EPA 16 PAHs. The mixed pine/polystyrene fuels produced substantially higher PAH loading than the biomass-only fuels. After a single exposure, the OS accumulated the highest total PAH mass, reaching 27.50±0.47 μg/100 cm2 (50/50 pine/PS), while repeated exposures (70/30 pine/PS) increased contamination across all layers, with the MB reaching 20.76±0.36 μg/100 cm2 and showing increased contributions from high-molecular-weight PAHs. After 7 days of storage, total PAHs decreased in the OS but increased in the inner layers (MB & TL), indicating redistribution of semi-volatile PAHs throughout the multilayer sample. Toxicity equivalent (TEQ) values were used as screening-level indicators of PAH hazard, not as direct estimates of exposure or health risk. Overall, these findings demonstrate that multilayer PPE is a dynamic reservoir for PAHs from combustion and a controlled standard for future studies on the persistence, transfer, and decontamination of PAHs.