An arc blast vent for an electrical equipment enclosure has a plate forming a part of the enclosure with triangular cutouts arranged within a regular polygonal area of the plate and having a frame of the plate material in between them. Substantially identical triangle shaped flaps, each having hold downs along and adjacent to a first leg of the triangle for attachment to the plate, and in from the first leg have a line of perforations through the triangle forming a weakened area for a deformable hinge. Each of the triangle shaped metal flaps have the second and third legs with their edges resting without tenacious engagement on the frame of the plate material.