Electronic equipment enclosures of the present disclosure are configured to house electronic equipment. The enclosures generally include vent opening configured to allow air to flow into and out of the enclosures, and fans configured to circulate the air within the enclosures around the electronic equipment housed therein. The enclosures also include backflow assemblies located between the vent openings and the fans, and configured to inhibit movement of unwanted materials through the enclosures between the vent openings and the fans. In addition, the backflow assemblies may include multiple vanes disposed adjacent the vent openings and arranged to block straight paths from the vent openings into the enclosures past the multiple vanes. The multiple vanes may be operable both to inhibit the movement of the unwanted materials through the enclosures and to allow air to flow out of the vent openings from the enclosures without moving.