Impact doors are lightweight rigid swing doors that are pushed open by a person or by a materials handling vehicle. Most impact doors are installed as double doors, which makes them easier to use. The doors themselves are typically made of plastic sheet materials over a light metal frame. The doors are installed in a strong frame that withstands the transmitted impact forces. Figure 1 shows an impact door in action. To minimize air leakage, the door can be equipped with effective seals on all sides. They can also be insulated to a limited extent. Doors that seal tightly provide a significant amount of noise isolation. Impact doors can be used by both people and vehicles. However, the door must have a fairly strong closing force to overcome the resistance of the seals. The closing force may be an impediment to some people on foot.