Abstract: The invention provides a filter mask for filtering air inhaled and exhaled from the mouth and nostrils while providing a positive facial lock at all edges of the mask. The filter mask has upper and lower edges which are provided with malleable stiffeners for conforming to the shape of the wearer's nose and cheek area and the lower jaw and chin area, respectively. The material of the filter mask is folded to have an omega pleat for forming a breathing chamber and a secondary pleat for assisting in securing the mask to the lower jaw and chin area. A pair of headbands are used to hold the mask on the head. The peripheral edges of the mask are bound. The mask provides excellent filtration since the positive facial lock around all edges of the mask substantially prevents air from leaking between the mask and the face.