Abstract: Expandable pleated air filters, reusable frames for such air filters, kits for making framed air filters, and methods of making and using framed air filters. The pleated air filter may have first and second non-corrugated ends that have first and second securing tabs that are configured to be inserted into first and second upward-open-ended elongate slots of a frame. The pleated air filter may have first and second corrugated edges at which first and second corrugated edges of a compliant nonwoven electret filter media of the pleated air filter extends outward beyond first and second corrugated edges of a stiffening layer of the pleated air filter, so that the first and second corrugated edges of the pleated air filter are self-sealing when abutted against inward sidewalls of a frame in which the pleated air filter is installed.

Abstract: Reusable frames for air filters, framed air filters, kits for making framed air filters, and methods of making and using framed air filters. The frame may include a frame base and a frame cover that are attached to each other to form the frame. The frame may include first and second opposing primary frame portions that respectively include first and second upward-open-ended elongate slots that are configured to receive first and second securing tabs of an expandable pleated air filter. The frame may include a set of upward struts that collectively form an upward anti-sag lattice with a multiplicity of anti-sag protrusions that protrude in a downward direction from a downward face of the upward anti-sag lattice.

Abstract: A method and system of determining air quality are disclosed. In examples, a method comprises identifying one or more aerosol particle types based on an absorbance spectra of aerosol particles captured on a filter and determining a mass concentration of each of the one or more aerosol particle types based on the absorbance spectra and the aerosol particle type. The method further comprises detecting a median particle size of each of the one or more aerosol particle types based on a rate of change of the absorbance spectra and the aerosol particle type. The method further comprises determining an air quality metric based on the identified one or more aerosol particle types, the determined mass concentration of each of the one or more aerosol particle types, and the determined median particle size of each of the one or more aerosol particle types.

Abstract: An air filter with an expandable pleated air filter media assembly and with first and second end frame pieces permanently attached to first and second ends of the pleated air filter media assembly; and, with first and second side frame pieces that are removably nested onto the first and second end frame pieces. The first and second side frame pieces can be removed from their nested positions on the first and second end frame pieces and mounted on first and second corrugated edges of the pleated air filter media assembly, whereupon the first and second side frame pieces, and the first and second end frame pieces, collectively form a perimeter support frame.

Abstract: A filter frame assembly includes a main frame including a first end and a second end, and a spindle unit disposed at the first end. The spindle unit includes a spindle frame, a dispensing spindle non-rotatably coupled to the spindle frame, and a receiving spindle rotatably coupled to the spindle frame. Each of the dispensing spindle and the receiving spindle is configured to receive a filter web thereon in a wound configuration. The main frame is insertable through a filter slot of an HVAC system from the second end, such that the main frame is at least partially received within the HVAC system and the spindle unit is disposed external to the HVAC system. The filter web extends from the dispensing spindle towards the second end of the main frame and extends back to the receiving spindle, while being at least partially received in the main frame.

Abstract: A method and system of determining a filter life are disclosed. In examples, a method comprises capturing aerosol particles on a filter and measuring absorbance spectra of the aerosol particles captured on the filter. The method further comprises identifying one or more aerosol particle types based on the measured absorbance spectra and determining a mass accumulation of each of the one or more aerosol particle types based on the measured absorbance spectra and the aerosol particle type. The method further comprises determining a median particle size of each of the one or more aerosol particle types based on the measured absorbance spectra and the aerosol particle type and determining a filter life based on the determined mass accumulation and the determined median particle size of each of the one or more aerosol particle types.

Abstract: A method and system of determining air quality are disclosed. In examples, a method comprises identifying one or more aerosol particle types based on an absorbance spectra of aerosol particles captured on a filter and determining a mass concentration of each of the one or more aerosol particle types based on the absorbance spectra and the aerosol particle type. The method further comprises detecting a median particle size of each of the one or more aerosol particle types based on a rate of change of the absorbance spectra and the aerosol particle type. The method further comprises determining an air quality metric based on the identified one or more aerosol particle types, the determined mass concentration of each of the one or more aerosol particle types, and the determined median particle size of each of the one or more aerosol particle types.

Abstract: A framed air filter that includes air filter media and a frame with four frame portions. At least one frame portion includes an inner sidewall and an outer sidewall that meet at a sidewall junction. The sidewall junction extends along a score line that includes at least one cut-scored segment and one crush-scored segment.

Abstract: A framed air filter that includes air filter media and a frame with four frame portions. At least one frame portion includes an inner sidewall and an outer sidewall that meet at a sidewall junction. The sidewall junction extends along a score line that includes at least one cut-scored segment and one crush-scored segment.