may be quickly and easily installed into an aperture in a vehicle 50 therefore the vehicle body aperture into which the pressure relief valve 10 is installed may be of a dimension much smaller than the actual size ingress side of the pressure relief valve 10 however the dimensions of the aperture in the vehicle body will be of the same general dimensions as the body flange 14 the preferred embodiment of the valve 10 is configured such that the walls 18 20 22 and 24 extend in a non perpendicular manner more particularly each of the walls 18 20 22 and 24 extend obliquely and will form an acute angle with the body flange 14 in this way vehicle cabin side of the voids 25 a 25 b will have an overall dimension greater than or equal to the aperture in the motor vehicle 50 wherein such aperture is defined to be no greater than the inner dimensions of the flange 12 in this way due to the venturii effect of the sloped walls of the pressure relief valve 10 the air flow through the valve 10 will be equal or nearly equal to that of an open aperture in the motor vehicle 50 with reference to fig6 a pressure relief valve 100 according to a second embodiment of the.