In gas filled porous media the local elevation of pressure slowly diffuses to the adjacent layers of gas inducing the rise in temperature there. In the case of explosive gases this mechanism may lead to the formation of a self-sustaining combustion wave propagating al a constant speed. It is argued that the barodiffusion may be responsible for the occurrence of the so-called high velocity regime often observed in filtration combustion. It is shown that the high velocity regime may emanate from the low velocity regime controlled by the system＇s thermal diffusivity. It is suggested that the effect may be related to the classical problem of deflagration-to-detonation transition in narrow pipes.