According to an embodiment, the backflow flap layer 204 comprises one or more backflow flaps 204a, 204b-204n hinged to rotate in a proximal direction in a normal state (see, e.g., FIG. 2). As such, the front support layer 202 and the first adhesive layer 203 are each shaped with a substantially same or similar profile to each other, whereby each includes respective through-holes configured (e.g., shaped and positioned) to permit proximal rotation of the backflow flaps 204a-204n of the backflow flap layer 204, when in the normal state, through the through-holes of the front support layer 202 and the first adhesive layer 203, when assembled together. According to the described function of the backflow preventer 200, the backflow flaps 204a-204n of the backflow flap layer 204 are structurally hinged to rotate in only the single proximal direction when in the normal state, i.e., responsive to the cooling airflow from a corresponding fan 112, while being supported at least in part by the front support layer 202. Thus, the backflow flaps 204a-204n are constrained from rotating in the distal, backflow direction. A hinge such as with the backflow flaps 204a-204n is often referred to as a “l(fā)iving hinge”, e.g., a thin flexible hinge made from the same material as the two rigid pieces it connects. According to an embodiment, the backflow flap layer 204 is itself composed of a layered or laminate structure such as, from front (proximal) to back (distal), a polyethylene film followed by an acrylic adhesive layer followed by a plastic (e.g., polycarbonate) base material, collectively on the order of 0.3 millimeters thick, for a non-limiting example. As such, functionally the front polyethylene film acting as a hinge point for the individual backflow flaps 204a-204n.