An air filtering device comprising a base with a first side having an air inlet and a second side having an air outlet, the air inlet being on the underside of the base; a fan mounted inside the base, between its first and its second side, such that it assists with drawing a volume of input air into the air inlet of the base and out wherein said fan is capable of moving air through said air outlet, pushing the volume of air through an air flow path defined by an outer sleeve and through an air filter also located in the air flow path; an air filter bag extending longitudinally from the base and in direct air flow communication with said air outlet and comprising an air flow surface area from which air exits said air filter bag when said device is in use; a substantially air impermeable outer sleeve comprising a first open end, a second open end, and an air flow path therebetween, wherein said outer sleeve longitudinally extends from the base and is in air flow communication with said air outlet, and wherein said outer sleeve envelops said air filter bag around its longitudinal axis and defines a spatial gap between said air filter bag and said outer sleeve, wherein the volume of air exiting said outer sleeve at said second open end is at least 60% of the air entering said outer sleeve at said first open end when the device is in use; wherein the device is configured to provide an air flow rate in said air flow path of 2.27 to 3.40 m 3 /min (80 to 120 CFM) and wherein the spatial gap provides a pressure drop of less than 8 Pa at said air flow rate, optionally wherein the air flow rate in said air flow path is 2.27 to 2.83 m 3 /min (80 to 100 CFM) and the pressure drop of said device is less than 8 Pa, and wherein said air flow surface area of said air filter bag comprises a lower region and an upper region positioned along a longitudinal axis, wherein the minimum spatial gap at said lower region is at least 3 mm and the minimum spatial gap at said upper region is at least 15 mm. a base with a first side having an air inlet and a second side having an air outlet, the air inlet being on the underside of the base; a fan mounted inside the base, between its first and its second side, such that it assists with drawing a volume of input air into the air inlet of the base and out wherein said fan is capable of moving air through said air outlet, pushing the volume of air through an air flow path defined by an outer sleeve and through an air filter also located in the air flow path; an air filter bag extending longitudinally from the base and in direct air flow communication with said air outlet and comprising an air flow surface area from which air exits said air filter bag when said device is in use; a substantially air impermeable outer sleeve comprising a first open end, a second open end, and an air flow path therebetween, wherein said outer sleeve longitudinally extends from the base and is in air flow communication with said air outlet, and wherein said outer sleeve envelops said air filter bag around its longitudinal axis and defines a spatial gap between said air filter bag and said outer sleeve, wherein the volume of air exiting said outer sleeve at said second open end is at least 60% of the air entering said outer sleeve at said first open end when the device is in use;