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From: Todd McGrath, (ASHRAE) Chair SSPC 52.2

Subject: Correction Regarding the Terms "MERV 17-20"

To Whom It May Concern,

I am writing to address a common misunderstanding regarding the terms "MERV 17-20" and provide clarification to ensure accurate information is given. As the current Chair of SSPC 52.2, I believe it is important to correct the usage of the terms “MERV 17-20”, as it is incorrect and may lead to

MERV ratings range from 1 to 16, with a higher number indicating a higher level of filtration efficiency. However, it is essential to note that the MERV scale ends at MERV 16. Currently, there is no officially recognized or standardized “MERV 17-20” value. Therefore, any reference to "MERV 17-20" would be inaccurate and potentially misleading.

I kindly request that you help spread awareness and correct any published “MERV 17-20” statements of this discrepancy and share this information with your colleagues, clients, or anyone who might be using the term "MERV 17-20." By doing so, we can prevent the perpetuation of incorrect terminology and promote accurate understanding within the industry.


Todd McGrath, Chair of ASHRAE Standard 52.2
Michael Corbat, President of National Air Filtration
Steven Nicholas, Waterloo Filtration Institute
Ken Winston, AFS