This latest study from UL FSRI investigates the efficacy of protective hoods and base layers in shielding structural firefighters from exposure to polycyclic aromatic hydrocarbons (PAHs), specifically naphthalene, during firefighting operations. Using mannequins dressed in various configurations of firefighter personal protective equipment (PPE), the study evaluates PAH ingress under controlled fireground simulation conditions. The focus is on naphthalene exposure as it primarily exists in vapor form in fireground environments.

Key Points

• 🛡️ Naphthalene Exposure: Naphthalene constituted 55% of total PAHs in the fireground environment and existed primarily in the vapor phase (92%).
• 🧥 PPE Configurations: Four PPE configurations were tested, ranging from standard knit hoods to particulate-blocking hoods with advanced interface controls.
• 🔬 Mannequin Testing: Filters and base layers on mannequins collected significant amounts of naphthalene, demonstrating partial protective effects of cotton base layers.
• 🔄 Particulate vs. Vapor: Vapor-phase contaminants like naphthalene more easily penetrated PPE, while particulate-phase PAHs were largely blocked.
• 📉 Evaporation Issues: Evaporative losses during sampling and processing likely led to underestimations of base layer effectiveness.
• 🔗 Interface Design: Enhanced interface designs, such as integrated hoods and liners, reduced PAH penetration compared to standard configurations.
• 🏋️ Static vs. Active Testing: Static mannequin models do not accurately simulate real-world firefighter movements and exposure scenarios.
• 📊 Measurement Discrepancies: Substrate-based sampling revealed lower attenuation of naphthalene than air sampling, suggesting substrate methods better capture skin exposure risks.
• 🧪 Biological Monitoring: Past studies indicate significant reductions in urinary PAH biomarkers with advanced PPE, supporting the importance of particulate-blocking designs.
• 🚒 Future Directions: Research should incorporate dynamic firefighter simulations, refined sampling techniques, and faster processing times to improve data accuracy and PPE design.

Conclusion

This research highlights that naphthalene, the most abundant PAH found in the firefighting environment (55% of total PAHs), readily penetrates both traditional knit and particulate-blocking hoods, although base layers like cotton turtlenecks reduce exposure somewhat. Mannequin tests showed a higher collection of naphthalene on under-layer filters compared to base layers, suggesting limited effectiveness of traditional fabrics in fully blocking vapor-phase contaminants. However, particulate-blocking hoods with advanced design features, like sealed interfaces and integrated liners, demonstrated a higher capacity to attenuate PAH exposure compared to traditional knit hoods.

The study underscores limitations in static mannequin tests, such as evaporative losses from sampling and the lack of firefighter movement. Results also show discrepancies between air sampling-based and substrate-based methods in estimating exposure risks, suggesting that substrate-based sampling may better reflect dermal absorption potential. The findings advocate for further research incorporating active firefighter simulations and advanced methodologies to enhance PPE effectiveness and firefighter safety.