Hydrogen gas driven permeation through the fine-grain graphites MPG-8 and R5710, and through CFC NB31 in two main directions has been investigated for sample thicknesses of 1–7mm and pressures from 10 −2 –10 Pa. The gas driven permeation occurs through the carbon-base materials by the hydrogen molecular gas flow through the internal porosity network rather than hydrogen atom diffusion through the graphite lattice. The permeabilities of MPG-8 and Nb31 are of the same order, while the permeability of R5710 is two orders of magnitude less. The specific bulk conductivity is about 5×10 15 moleculess −1 m −1 Pa −1 for MPG-8; 8×10 13 moleculess −1 m −1 Pa −1 for R5710; 1×10 16 moleculess −1 m −1 Pa −1 for Nb31 along ex-pitch (x) fibers after taking into account the perforated surface layer and 0.8×10 16 moleculess −1 m −1 Pa −1 for Nb31 along needled (z) fibers.