MERV Ratings

MERV RatingsMERV stands for "Minimum Efficiency Reporting Value". It is a measurement scale designed by the ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The independent scale allows for accuracy in measuring a filters ability to capture contaminates. This can help gauge needs for health and costs.

For example, according to "Residential Air Cleaners (2nd Edition): A Summary of Available Information", a HEPA filter is often impractical in central HVAC systems due to the large pressure drop the dense filter material causes. Experiments indicate that less obstructive, medium-efficiency filters of MERV 7 to 13 are almost as effective as true HEPA filters at removing allergens, with much lower associated system and operating costs. The table below shows various MERV ratings and their typical applications.

MERVMin. particle sizeTypical controlled contaminantTypical Application
1–4 > 10.0 μm Pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers, carpet fibers Residential window AC units
5–8 10.0–3.0 μm Mold, spores, dust mite debris, cat and dog dander, hair spray, fabric protector, dusting aids, pudding mix Better residential, general commercial, industrial workspaces
9–12 3.0–1.0 μm Legionella, Humidifier dust, Lead dust, Milled flour, Auto emission particulates, Nebulizer droplets Superior residential, better commercial, hospital laboratories
13–16 1.0–0.3 μm Bacteria, droplet nuclei (sneeze), cooking oil, most smoke and insecticide dust, most face powder, most paint pigments hospital & general surgery