Theoretical analysis, modeling, and simulation are used to provide insight into the development of permeability during thermal damage of the high explosive PBX 9501. In a recently, published article. Terrones et al. [1] conclude that samples of PBX 9501 thermally damaged at 186 degrees C are not permeable to gas flow in a manner consistent with Darcy's Law. We disagree with their conclusion. We show that they have misreported data from the literature, and that their argument depends on a fluid flow model that is physically incorrect and is applied with inappropriate physical parameters.