The problem of attenuation of a shock wave during its propagation in long communication channels of industrial buildings or mining workings is considered. It is shown that an explosion in a channel produces a head shock wave with a plane wavefront, where the dynamic pressure significantly exceeds the pressure at fronts forming by the incident and reflected shock waves. A physical model of the formation and propagation of a shock wave in a channel with walls of different rigidity is proposed. It is shown that if one of the channel walls is movable or easily deformed, this leads to a violation of geometry of plane wavefront of the head shock wave and its weakening. The necessity of arranging pressure-relief structure in communication channels of buildings with increased explosive hazard and mine workings is grounded.