A particle filtration system that includes first, second and third filter segments that each include several first, second and third filters. Each first, second and third filter includes a fibrous layer sandwiched between a pair of surface or outer layers. The range of pore sizes of each first, second and third filter varies according to the density of the surface layers relative to the fibrous layers.

Fibrous filter medium that includes a surface-loading filter layer comprising fine fibers having an average diameter of less than 1 micron; a depth loading filter layer; and a support layer; wherein the layers are configured and arranged for placement in a gas stream with the surface loading filter layer being the most upstream layer.

Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is a substituted-benzoic acid or a substituted-benzoate salt. The benzoic acid and benzoate salts are substituted by a hydroxyl or amino group at the ortho position or 1 position of the benzene ring. The benzene ring may contain additional substituent groups. The substituted-benzoate salt may have a monovalent, divalent, or trivalent metal counteraction.

Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is a substituted- or unsubstituted benzoate salt. The substituted benzoate salts are substituted by a hydroxyl group. The substituted-benzoate salt may have a divalent metal countercation.

This disclosure describes a high performing (including, for example, high efficiency and low pressure drop) filter media. The filter media includes a support layer and a layer of fine fibers wherein at least some of the fine fibers in the fine fiber layer having an average diameter at least 3 times the average fiber diameter of a smaller fine fiber in the fine fiber layer. The fine fiber layer may include multiple layers of fine fibers. In some aspects, the smaller fine fiber may be present in the same layer of fine fibers as the larger fine fibers. Additionally or alternatively, the larger fine fibers may be present in a first layer of fine fibers and the smaller fine fibers may be present in a second layer of fine fibers.

Fine fiber products including fiber webs, as well as related assemblies, systems and methods, are described. In some embodiments, fiber webs described herein may include fine fibers and relatively low amounts of degraded polymer formed during a fiber extrusion process. The fiber webs may be used for filter media applications.

A particle filtration system that includes first, second and third filter segments that each include several first, second and third filters. Each first, second and third filter includes a fibrous layer sandwiched between a pair of surface or outer layers. The range of pore sizes of each first, second and third filter varies according to the density of the surface layers relative to the fibrous layers.

An apparatus and a method are provided for a heating, ventilation, and air conditioning (HVAC) home air filter to remove airborne molecular contaminants and volatile organic compounds (VOCs) from air within residential spaces. The HVAC home air filter includes a supportive frame having a shape and size suitable to orient the HVAC home air filter within a residential HVAC system. A filter medium is retained within the supportive frame to remove the airborne molecular contaminants and VOCs from air flowing through the residential HVAC system. The filter medium includes a combination of media layers configured to exhibit a relatively high filtration efficiency and a low air pressure drop across the filter medium. The supportive frame includes a plurality of elongate sections and corner sections disposed along perimeter edges of the filter medium to support the filter medium within the residential HVAC system so as direct air through the filter medium.

A deaerator includes gas nucleation media and a porous barrier. The deaerator may include growth media between the gas nucleation media and the porous barrier. The deaerator may be part of a system for removing gas from a fluid, where the system includes a tank with a fluid inlet and a fluid outlet and having a fluid flow path from the fluid inlet to the fluid outlet, and where the deaerator is in the fluid flow path. A method for removing gas from a fluid includes passing the fluid through the deaerator defining a fluid flow path.

A relofted, spunbonded nonwoven web exhibiting a solidity of from less than 8.0%, to at least 3.0%, and exhibiting a Quality Factor of at least 0.30. Methods of making a relofted web; and, methods of using a relofted web as an air-filtration web, e.g. as a filter media or a layer thereof.