Filtration Efficiency and Pressure Drops

filtration efficiency


I just read the very excellent article in the ACHR NEWS about HVAC systems and the spread of COVID-19. The article is a conversation from experts from Johnson Controls, Trane, and ASHRAE. Pretty good talent there!


If you haven’t read it, please do. Basically the conversation discusses HVAC, airflow, and the recommended solutions for controlling IAQ for health. As has been often told by ASHRAE, ventilation is king. And keeping the system operating efficiently through high-efficiency filtration. Humidity control is also mentioned as an important component that sometimes gets overlooked (but shouldn’t ever) as it relates to virus protection.


Filtration Efficiency and Pressure Drops


One note of particular importance that was missing from the filtration conversation is that of higher MERV filters. These help trap more airborne contaminants and do a better job of protecting the HVAC system.  And as our own John Bloemer, Executive Consultant and Engineering Fellow reminds us, the MERV conversation is an opportunity to provide both.


“Installing a 4” filter provides lower pressure drop even at higher MERV ratings, up to a MERV 16, over ANY 1” or 2” filter”, John reminds us.  “If a homeowner has a 1” filter they may have limited options for increased filtration efficiency, but working with their HVAC professional we can provide very low-pressure drop at higher filtration levels”.

pressure drops over time

Air Flow Increases in Larger Filters


John continues, “Think of media as a straw.  The bigger the straw the easier it is to get water through it (or air in this case). Same thing with a water hose.


Increasing the amount of media by increasing its depth (4” vs 1”) makes it is easier to get the air through the filter and also increase filtration efficiency.  With the overall size of Aprilaire Media Air Cleaner cabinets, you can provide some of the highest filter efficiencies at the lowest pressure drops on the market”.


Aprilaire MERV 16 4” filters create a lower pressure drop than a 1” MERV 8.  Higher efficiency does not have to mean higher pressure drops.  An added bonus: 4” filters last 3-4 times longer than a 1” filter, so fewer changeouts, and fewer callbacks.