What do the different filter ratings mean? HEPA, MERV, 95%…?

Filters are rated on their efficiency to stop and trap particulate of a particular size. Most filters used in Ace extractors base their efficiency rating on stopping particulate of 5 microns or greater. A micron is 1/25,400th of an inch in diameter, and most carbon steel welding particulate is approximately 5% microns in size. So an Ace 95% filter will stop and trap 95% of particulate 5 microns or greater in size, effectively stopping most carbon steel welding particulate while still achieving high airflow performance.

Ace HEPA filters, on the other hand, stop and trap 99.97% of particulate .3 micron in size or greater. This filter is particularly effective is capturing Hexavalent Chromium in stainless steel welding processes, because chromium particulate is much smaller in size than carbon steel welding particulate.

In addition to above efficiency ratings, Ace now shows an equivalent MERV rating on many of its product literature and on this website.  MERV, which is an acronym for Minimum Efficiency Reporting Value, is a rating devloped for use by the HVAC industry.  However, in recent years some of Ace’s competitors have used the MERV system to represent their filter ratings, so to facilitate the process of fair comparison between Ace’s and competitors’ products, we now provide our filters’ MERV ratings along with our standard efficiency ratings.

The MERV rating system assigns a number between 1 and 20 to filters of varying efficincies, 1 being the least efficient with 20 being the most efficient.  The most common Ace filters are listed in the chart that follows (click on link), along with their corresponding efficiency and MERV ratings.  Use this guide to determine the correct filter for use in your work application, but when in doubt, please contact your Ace representative or the factory.

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