A flat air filter element for an air filter has a filter medium of cellulose material and a sealing element extending circumferentially about the filter medium. Sealing element and filter medium have at least one recess at an outer contour of the flat air filter element. The sealing element has a circumferentially extending holding groove to be engaged by a housing part of a filter housing. The filter housing has a housing pot, a housing cover to cover the housing pot, and a closure element for closing the filter housing. The flat air filter element is secured in the closed state of the filter housing by circumferentially clamping the sealing element between housing pot and housing cover. The circumferentially extending holding groove of the sealing element is engaged by housing pot or housing cover. The closure element of the filter housing is arranged in the region of the recess.

An indoor unit includes axial-flow fans, which are provided on downstream of an air inlet. Further, a plurality of first bars are provided to the air inlet. In plan view, leading edge portions of blades of the axial-flow fan are inclined in a direction of rotation of the axial-flow fan from a rotary shaft side of the axial-flow fan to an outer peripheral side. Further, in plan view, the plurality of the first bars are inclined in a direction opposite to the direction of rotation of the axial-flow fan from the rotary shaft side of the axial-flow fan to the outer peripheral side.

An air box assembly attached to an outdoor power tool for reducing sound generated by an engine is provided. The air box assembly includes a casing formed as an upper and lower housing attached to each other to define an enclosed space. The casing includes at least one air inlet and an air outlet. At least one filter is positioned within the casing. An air guide assembly is positioned within the casing such that the flow of air to the engine passes through the air guide assembly as it travels to the engine and sound from the engine passes through the air guide assembly as it exits the air box assembly. The air guide assembly includes a plurality of fluid pathways therein, wherein the fluid pathways are in fluid communication with the air outlet of the air box assembly.

A silencer for an exhaust gas system of a motor vehicle has an external housing that has at least one inlet opening and at least one outlet opening for exhaust gas. The silencer includes a silencer chamber and a filter monolith through which exhaust gas flows, and which is circumferentially surrounded by the silencer chamber. Also disclosed is a motor vehicle with at least one silencer.

A filter element is provided with a filter bellows that has an inflow side and an outflow side for a fluid to be filtered, wherein the filter bellows is made of a zigzag-folded filter medium with folds with fold edges. The inflow side is defined by the fold edges of the folds of the zigzag-folded filter medium at the inflow side and the outflow side is defined by the fold edges of the folds of the zigzag-folded filter medium at the outflow side. At least one filter element holding device is provided that holds the filter element in a filter housing. The at least one filter element holding device is connected directly or indirectly with the filter bellows. At least one supporting element supports the filter element in the filter housing; the at least one supporting element is separate from the at least one filter element holding device.

The air filter device includes a main member, a conduit member, a sealing piece, a pressurizing piece, a filter element, and a cap. The conduit member, sealing piece, pressurizing piece, and filter element are sequentially stacked in the main member. The conduit member provides a spiral duct with a second inlet and a second outlet. The second inlet is conducted to an outlet opening of the pressurizing piece. The second outlet is conducted to a plug extended from a bottom side of the main member. The cap is fastened to the main member with airflow paths between the cap and main member. The main member may be joined to the inlet terminal of any air compressor. External air is drawn into the air compressor through the filter element, pressuring element, conduit member, and the plug so as to achieve smooth, steady, and quiet air intake.

Systems and Apparatus for a personal ventilation system that provides a personalized column of clean air surrounding a user's space is presented. The personal ventilation system includes an air purifier with a fan and an annular gap downstream of the fan. The annular gap has an inner radius that is within 95% of the outer radius. The annular gap structure allows the air purifier to produce a column of air with an entrainment ratio lower than other commercially available fan. At a distance of 1.5 meters, the air purifier is configured to have an entrainment ratio of lower than 40%. The air purifier also has a removable filter located upstream of the fan. The ventilation system is capable of delivering highly-localized filtered air to a user or location.

A filter element for a filter system has a hollow cylinder-type filter bellows with an end face and a substantially closed bottom provided thereat. At least one resonator structure provided at the bottom provides noise attenuation of a flowing fluid. The resonator structure has two or more grooves arranged at an outer side of the bottom and separated from each other by a partition. At least one of the grooves is connected in fluid communication through an opening to an interior of the filter element. The resonator structure, when installed in a filter housing of the filter system as intended, seals tightly relative to a complementary resonator structure of the filter housing. The grooves are connected in fluid communication through connection openings arranged in the resonator structure of the filter element and/or the complementary resonator structure of the filter housing. A filter system with such a filter element is provided.

A filter system for filtering a fluid has a filter housing with housing top part and housing bottom part, wherein the housing top and bottom parts extend along a housing axis. A filter pack arranged in the filter housing separates fluid-tightly a clean fluid side and a raw fluid side from each other. The filter pack has a filter element with a hollow cylinder-type filter bellows arranged about a longitudinal axis of the filter element. The filter element has a first substantially closed end face and a first end disk arranged thereat, wherein the first end disk is positioned opposite a second end disk of the filter element. The second end disk has a fluid passage for filtered fluid. A resonator with an end closed by a bottom is arranged inside the filter pack such that the bottom is oriented toward the first end disk of the filter element.

A sound attenuator for a separator device for gas and a separator device are described. The sound attenuator comprises at least one tubular member having at least one gas inlet opening in the area of one end and at least one gas outlet opening in the area of the other end. The at least one gas outlet opening is placed in the circumferential wall of the at least one tubular member near the one end and the end face at this end of the at least one tubular member is closed by a closing part.