Don Thornburg Director of R&D, Camfil Farr Don has chaired numerous committees, including 52.2 promoting improved air filtration for industry users. The History of HVAC Air Filter Testing In the filtration industry it is common to use laboratory testing to evaluate air filter performance. However, the laboratory is not where the filter is used and thus “real life” performance is much more important. In addition, there is a big difference between Cleanroom or HEPA filter testing and HVAC (Heating Ventilation and Air Conditioning) filter testing. All true HEPA filters are individually tested as part of the manufacturing process. If the filter does not meet the minimum requirements, the filter can sometimes be repaired or it is scrapped. HVAC filters are not individually tested and are assumed to meet the performance level shown in the published literature. For Camfil Farr, HVAC filter testing is continuous throughout the life of the product in one of our many R&D facilities around the world. However, there are companies who never test their products and simply copy the literature performance of Camfil Farr or other manufacturers, and then sell the product. Most filtration users do not realize these issues are in this industry and assume the literature result and actual result will be the same. Expecting to get the same filtration performance of an HVAC product in a laboratory test would be like actually getting the 35mpg that was on the sticker when you bought that last car – remember “actual mileage may vary”. With cars or with air filters, some products do deliver the promised performance, but some are not even close. In this discussion, we will look at why these differences exist by examining the current air filtration standards, where they came from, where they are going, and what needs to be fixed along the way. Why Air Filters The first question to ask is why do you use an air filter? Is it to save energy, to fill a hole in the air handler unit (AHU), or is it to remove particulate from the air? The first two items are attributes of an air filter; the last one is a requirement. This is a very important distinction and must be understood by the filter user. If saving energy is the only goal, take the filters out and call it a day. The cost of moving air through an AHU is directly related to the resistance to airflow of the items and components in that AHU. If you remove the air filters, the resistance will go down and the cost of the energy to move the air will go down in most systems. However, the particulate and contaminants in the airstream will remain and/or settle in places the owner does not want – on the equipment or worse yet, contaminating the product. Obviously, this is of major concern in the Pharmaceutical industry. HVAC Air Filter Standards The filtration industry is inundated with multiple filtration standards to classify, identify, and evaluate various performance characteristics of an air Air Filters Testing Standards Comparison ASHRAE Standard 52.2-2007B Minimum Efficiency Reporting Value MERV ASHRAE 52.1-1992 Composite Average Particle Size Efficiency, % in Size Range, microns EN 779 2002 Average Arrestance Average Dust Spot Efficiency Average Efficiency at 0.4 micron % Range 1 Range 2 Range 3 0.30 - 1.0 1.0 - 3.0 3.0 - 10.0 % % 1 n/a n/a E3 < 20 Aavg ≥ 65 < 20 G1 A<65 2 n/a n/a E3 < 20 Aavg ≥ 65 < 20 G2 65< A ≤80 3 n/a n/a E3 < 20 Aavg ≥ 70 < 20 4 n/a n/a E3 < 20 Aavg ≥ 75 < 20 5 n/a n/a E3 ≥ 20 80 20 6 n/a n/a E3 ≥ 35 85 20-25 7 n/a n/a E3 ≥ 50 90 25-30 8 n/a n/a E3 ≥ 70 92 30-35 G3 80< A ≤90 9 n/a n/a E3 ≥ 85 95 40-45 10 n/a E2 ≥ 50 E3 ≥ 85 96 50-55 11 n/a E2 ≥ 65 E3 ≥ 85 97 60-65 12 n/a E2 ≥ 80 E3 ≥ 90 98 70-75 G4 90< A F5 40< E ≤60 F6 60< E ≤80 13 n/a E2 ≥ 90 E3 ≥ 90 98 80-85 F7 80< E ≤90 14 E1 ≥ 75 E2 ≥ 90 E3 ≥ 90 99 90-95 F8 90< E ≤95 15 E1 ≥ 85 E2 ≥ 90 E3 ≥ 90 99 95 F9 95< E 16 E1 ≥ 95 E2 ≥ 95 E3 ≥ 95 100 99 H10 Note: The final MERV value is the highest MERV where the filter data meets all requirements of that MERV. Camfil Farr 15