The flame propagation of inflammable media is very similar to the law of fluid flow. The flame disperses all around according to certain speed of propagation and it is the resistance of propagation to influence the speed of propagation. The explosion-proof material has highly porous structure so the pores of material can decompose the propagation energy of flame, and simultaneously, the highly porous structure can greatly increase the resistance of flame propagation, therefore, the pore size has decided the resistance of flame propagation and speed of propagation. Larger pore size means faster speed of propagation and smaller pore size means slower speed of propagation, so the flame propagation may be stopped when the pore size is decreased to certain limit. This flame flow explosion-proof porous blocking effect is called as the blocking effect of material, which can directly influence the explosion-proof effect of material