One of the major mechanisms of deactivating spores is to expose them to elevated temperatures. Experiments carried out in an exposure tube to study the effects on spores in a high temperature gas environment provide evidence of spore deactivation, although the deactivation mechanism is not clear. It was found that the time constant associated with heat transfer was smaller than the exposure time by more than an order of magnitude. In this work, we study the conduction of heat from a high temperature gas to fractal-like aggregates of spores. Due to the complex geometry of the aggregates, many of the spores are shielded by other exposed spores, thus having an increased time constant associated with heat conduction from the high temperature gas. Thus, in the proposed work, we carry out a quantitative analysis of the shielding effect in fractal-like aggregates of spores resulting in a spatial variation of gas to spore heat transfer coefficient.