A blast diffuser for a structure may include a diffuser assembly. The diffuser assembly may include a plurality of vanes arranged in spaced relation to one anther. The vanes may be configured to redirect airflow of an overpressure wave from a first direction toward the diffuser assembly to a second direction generally parallel to the structure. The vanes may be offset from the structure by an offset distance forming a gap for the airflow between the vanes and the structure.