AIR FILTRATION SYSTEM

摘要

A composite gas filtration system for removal of toxic or harmful agents from a breathable gas supply, wherein a compressor fed pressure swing adsorption unit is placed upstream of an adsorbent carbon filter unit in a gas supply line, characterised in that a plenum chamber is positioned in the gas supply line with one or more inlet orifices supplied by gas treated by the pressure swing adsorption unit, one or more exit orifices leading to the carbon filter unit, and one or more further inlet orifices supplied by gas from upstream of the pressure swing adsorption unit, wherein a means for drawing or propelling breathable gas through the plenum chamber and carbon filter from the further inlet orifices in the event of shut down of the pressure swing adsorption unit and/or compressor is provided. By use of the preferred system of the present invention it is thus possible to operate a high pressure swing adsorption unit in conjunction with an adsorbent carbon filter unit, that not being of high pressure type, whereby in event of the high pressure units failing the system automatically switches to a back-up mode, without the need for electronic components if sprung plates or similar mechanical valve means are used, said back-up mode not requiring redundant units that would be required in prior art systems.