Xu et al. reported the glass transition temperature and viscosity of unaged and aged BBOA generated from the combustion of pine wood, poplar wood, cedar wood and cornstalk using flaming conditions. Glass transition temperatures and viscosities were calculated from volatility measurements, which assumes that the BBOA particles contained a single phase. At 35% RH and 298.15 K, the viscosities of those unaged samples ranged from 9.95×10 4 to 4.22×10 Pa s. After aging using an OH exposure equivalent to 1.5 days in the atmosphere, the viscosities of the BBOA from wood fuels increase by factors of 2.5 to 13. The viscosity of BBOA from burnt cornstalk was halved after the same aging time. Nevertheless, even after aging, the viscosity of the laboratorygenerated BBOA was orders of magnitude less viscous than our field BBOA samples at 30-40% RH.