ARLINGTON, Va. - The Air Conditioning Contractors of America (ACCA) has released the latest in its series of technical bulletins for members. The bulletin, called “Filtration - A Primer,” explores the basics of filters, including how HVAC equipment modifications are often required when a filter change results in increased system pressure drop through increased filter resistance.

ACCA notes that filters are designed to remove particulate contaminants from the air. While most airborne particles are harmless, some - like microorganisms, droplet nuclei, and spores from fungi - can cause allergic reactions or illness in some people. However, most HVAC systems are designed to utilize basic filtration aimed at protecting coils and heat exchangers from relatively large dust particulates. For environmental and occupant health concerns, a higher level of filtration needs to be included in the system design.

ACCA technical bulletins may be downloaded by members at For more information, contact Don Prather at

Publication date:11/30/2009