Active air sampling and TD-GC-MS analysis of toxic combustion products of OSB in well-ventilated and under-ventilated fire conditions

Oriented Strand Board (OSB), a wood composite which is engineered by compressing wood strands and adhesives into panels, is commonly used in both commercial and residential construction. As such, the mechanical and thermal properties of the material have been studied extensively, particularly in terms of its fire resistance performance. Understanding the products of combustion from OSB is important to inform fire models and predict survivability conditions and fire growth. Many studies have focused on measuring small molecules such as H₂O, CO, CO₂, and CH₄ in effluent, however, the literature does not adequately address other toxic species produced from OSB such as volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) under different combustion conditions. The equivalence ratio (Φ), a parameter which describes the ratio of fuel to oxygen in a fire, is often used to investigate the thermal properties of materials, including the prediction of toxic combustion product yields. For Φ > 1, a fire is considered fuel-rich, and it forms more products of incomplete combustion, whereas Φ < 1 is fuel-lean and complete combustion occurs, forming fewer toxic species. This study utilized active air sampling paired with thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to quantitate the yields of VOCs and PAHs in the effluent of OSB burned under three different equivalence ratios representing well-ventilated and under-ventilated fire conditions.

The Fire Propagation Apparatus was used to burn OSB with Φ = 0.5, 1.0, and 1.5. A heated stainless-steel apparatus sampled the effluent onto four thermal desorption tubes in parallel. The flow rate through each tube was adjusted between 50 and 400 mL/min to achieve the desired concentrations of VOCs and PAHS on the tube while avoiding breakthrough. Calibration curves were used to quantitate benzene, toluene, ethylbenzene, xylene, styrene, naphthalene, pyrene, and benzo[a]pyrene in the effluent. The results show that the total concentration of VOCs and PAHs increases with the equivalence ratio. Across all equivalence ratios, benzene is the largest VOC contributor, followed by toluene. PAH concentrations increase significantly at Φ = 1.5, and both low molecular weight and high molecular weight PAHs are identified in the effluent. This work demonstrates a robust and adaptable active air sampling technique paired with TD-GC-MS analysis for toxic products of combustion in fire effluent.