Abstract: An intra-oral filtering device for filtering and removing noxious materials from the air during the breathing process includes a housing having a cavity portion therein which contains a filter material for removing noxious materials from the air during the breathing process. The housing includes a mouth-piece portion and an exit portion communicating with the cavity portion to provide a path of travel for the air during the breathing process. The exit portion includes an unidirectional valve cover which permits purified air to pass through the intra-oral filtering device and which prevents saliva and expelled air from entering the intra-oral device through the exit portion.