A filtration mask has a collapsible air guide and two filter supports connected at a hinge. The filter supports are movable between a storage position and a deployment position in which the angle between the filter supports being less in the deployment position than in the storage position. In an aspect of this invention, the filter support each have a recess at the hinging edge, and an exhale valve communicating with the air guide is mounted in the recess. In another aspect the exhale valve is connected to the filter supports by a flexible membrane. In a third aspect the air guide is formed by hinged panels.