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In many applications it is necessary to calculate heat transfer between aerosolized nanoparticles and the surrounding gas, for example when inferring particle sizes from time-resolved laser-induced incandescence (TiRe-LII) data. Under transition regime conditions the heat transfer rate from the aerosolized nanoparticles is often approximated using Fuchs’s boundary-sphere method, in which the problem domain is subdivided into a collisionless shell surrounding the nanoparticle that represents the Knudsen layer, surrounded by a continuum gas. Traditionally the collisionless shell thickness is set equal to the mean free path at the boundary sphere temperature, but recently several LII practitioners have adopted a more complex treatment that accounts for particle curvature and the directional distribution of incident gas molecules. This paper assesses this approach using Direct Simulation Monte Carlo (DSMC); while this approach accurately represents the true Knudsen layer thickness, it does not improve the accuracy of heat conduction rates under conditions typical of LII experiments.