Air Filter Terms & Abbreviations

Filter Types

  • ASHRAE Filters - Filters rated using ASHRAE 52.2 standard

  • Bag Filter / Pocket Filter - Flexible, high-capacity filters used in large systems

  • Box Filter / Rigid Filter - Durable filters with rigid frames, often high-MERV

  • Carbon Filter - Uses activated carbon to remove gases and odors

  • Electrostatic Filter - Uses static electricity to attract particles

  • Final Filter - Main filter in a multi-stage system, captures finer particles

  • Gas-Phase - Air Filtration targeting gaseous pollutants, often using activated carbon or other adsorbent media

  • HEPA - High-Efficiency Particulate Air

  • MERV - Minimum Efficiency Reporting Value

  • Panel Filter - Flat panel design, often used as pre-filters

  • Pleated Filter - Filter with folds to increase surface area

  • Pre-Filter - Captures larger particles to protect final filters

  • ULPA - Ultra-Low Penetration Air

Performance & Standards

  • ACH - Air changes per hour

  • Adsorption - Process where gases, vapors, or dissolved substances adhere to the surface of a solid (typically activated carbon) used in air filters for odor and chemical removal

  • Appendix J - Testing protocol to determine filter efficiency in removing various particle sizes as the filter becomes dust loaded

  • Bypass - Unintended flow of unfiltered air around a filter, reducing system efficiency and compromising IAQ

  • CFM - Cubic Feet per Minute (airflow measurement)

  • Downstream - Area of HVAC system located after a filter; the leaving air/clean side of a filter

  • DP - Differential Pressure (pressure drop across a filter)

  • Dust Holding Capacity - Amount of particulate a filter can hold before replacement

  • Efficiency - The percentage of airborne particles a filter can remove from the air passing through

  • Initial Resistance - Pressure drop when the filter is new

  • MERV 1-16 - ASHRAE scale for particulate removal efficiency

  • PM - Particulate matter (e.g., PM2.5 = particles <2.5 microns)

  • MPR - Microparticle performance rating

Regulatory Bodies

Filter Components

  • Activated Carbon - Porous material used for odor/gas removal

  • Antimicrobial Coating - Helps reduce microbial growth

  • Fiberglass - Traditional media for low-cost filters made with glass fibers

  • Frame - The structural border, typically cardboard, plastic, or metal

  • Media - The fibrous material that captures particles

  • Spun bond - Durable non-woven synthetic filter media

Applications

  • Aerosol - Liquid or solid airborne particles suspended in air, gas, or vapor

  • AHU - Air Handling Unit

  • Bioaerosol - Suspension of airborne particles of biological origin, such as bacteria, viruses, mold, spores, or pollen

  • Cleanroom - Controlled environment with very low levels of pollutants

  • Containment - Use of filters during renovation/construction in occupied spaces

  • HVAC - Heating, Ventilation, and Air Conditioning

  • IAQ - Indoor Air Quality

  • RTU - Rooftop Unit