Experiments were carried out in a smog chamber to investigate the oxidation of levoglucosan in biomass burning particles exposed to gas-phase hydroxyl radicals (OH). The experiments featured atmospherically-relevant particle and oxidant concentrations and both high and low relative humidity conditions. In every experiment, we observed levoglucosan decay in particles exposed to OH. The extent of decay ranged from ˜20% to ˜90% and was strongly correlated to the integrated OH exposure. Increased relative humidity did not enhance or impede reaction. Relative kinetics indicate that levoglucosan has an atmospheric lifetime of 0.7-2.2 days when biomass burning particles are exposed to 1 × 106 molecules cm-3 of OH (typical average summertime conditions). This implies that levoglucosan reacts with OH on a timescale similar to that of transport and deposition, which has important implications for the use of levoglucosan as a tracer for biomass burning emissions in source apportionment studies.