Patent ID: 8641794

Claim:
A gas filtration apparatus comprising: (a) a substantially planar gas filter having a filter frame with substantially parallel front and rear faces and first and second peripheral edges on a perimeter of the filter, and filtration media within the filter frame, wherein at least the first filter frame edge is substantially planar and is aligned relative to the front face at an angle substantially greater than 90 degrees, and aligned relative to the rear face at an angle substantially less than 90 degrees; (b) a gas filter receptacle frame having at least one sidewall defining a substantially planar void into which the filter is inserted in a direction substantially parallel to a plane of the filter, when the filter is inserted in a desired orientation, for maintaining the gas filter in a path of gas flow; and (c) an obstruction formed on said at least one receptacle frame sidewall for accommodating the first edge of the filter frame during insertion of the filter into the void in the desired orientation of the filter, and for interfering with the second edge of the filter frame during insertion of the filter into the void in an undesired orientation of the filter.