Filtering Mask Assembly

A filtering mask assembly configured to be placed over the mouth and nose of the face of a wearer, the mask assembly comprising:

• (a) a housing comprising a fan and an outlet valve;
• (b) a filter releasably mounted onto the housing and adapted to substantially follow a shape and contour of said housing to seal the housing from the environment;
• (c) a face seal interposed between the wearer's face and the housing to provide a resilient conformity to the wearer's face when the mask assembly is worn;
• said filtering mask assembly defining an inner space between the mouth and nose of the wearer and an inner side of the mask assembly, an intermediate space between the housing and the filter, and an outer space separated from the inner space by said mask assembly,
• wherein the fan is positioned on a downstream side of said filter to draw air through said filter, and the fan comprises a fan casing having an air inlet facing said filter and communicating with the intermediate space between the filter and the housing, and an air outlet coaxially opposite the air inlet and communicating with the inner space of the mask assembly,
• wherein an inner diameter of the fan casing is adapted to taper from the inlet towards the outlet to generate a pressure increase from the inlet towards the outlet to compensate for a pressure drop through the filter, and
• wherein, when in use, the outlet valve is adapted to open to expel substantially all the exhaled air from said inner space to said outer space when air pressure inside said inner space is greater than air pressure is said outer space and to remain closed when the pressure in the inner space is lower than the pressure in said outer space, thereby preventing the breathing of any air which has not passed through said filter.