The re-ignition potential of partially burnt wood-based embers was investigated theoretically by studying their extinction characteristics. An adaptation of Semenov’s thermal explosion theory was used in conjunction with a linear stability analysis to determine the critical particle size at which extinction occurs. Particles of various shapes were studied and the analysis was carried out for both thermally thin and thermally thick particles. The results of our analysis indicate that thermally thick embers are less susceptible to extinction than thermally thin ones and, as such, are more prone to re-ignition. The results also show that the extinction of wood embers is strongly affected by the particle temperature, particle shape, and reaction kinetics. The effects of ambient conditions were found to be less pronounced than particle properties.