Minimum Efficiency Reporting Value
Encyclopedia
Minimum efficiency reporting value, commonly known as MERV rating is a measurement scale designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers
(ASHRAE) to rate the effectiveness of air filters. The scale "represents a quantum leap in the precision and accuracy of air-cleaner ratings" and allows for improved health, reduced cost and energy efficiency in heating, ventilation and air conditioning (HVAC)
design. For example, 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 scale is designed to represent the worst case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometre
s. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range.
Below is a table of example MERV ratings:
American Society of Heating, Refrigerating and Air-Conditioning Engineers
The American Society of Heating, Refrigerating and Air Conditioning Engineers is an international technical society for all individuals and organizations interested in heating, ventilation, air-conditioning, and refrigeration...
(ASHRAE) to rate the effectiveness of air filters. The scale "represents a quantum leap in the precision and accuracy of air-cleaner ratings" and allows for improved health, reduced cost and energy efficiency in heating, ventilation and air conditioning (HVAC)
HVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
design. For example, a HEPA
HEPA
High-Efficiency Particulate Air or HEPA is a type of air filter. Filters that are awarded the HEPA accolade are used in various locations, whether in medical facilities, automotive vehicles, airplanes, home filters, or wherever very pure air is sought. The filter must satisfy certain standards of...
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 scale is designed to represent the worst case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s. The MERV rating is from 1 to 16. Higher MERV ratings correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range.
Below is a table of example MERV ratings:
| MERV | Min. particle size | Typical controlled contaminant | Typical Application |
|---|---|---|---|
| 17–20 | < 0.3 μm | Virus, carbon dust, sea salt, smoke | Electronics & pharmaceutical manufacturing cleanroom |
| 13–16 | 0.3–1.0 μm | Bacteria, droplet nuclei (sneeze), cooking oil, most smoke and insecticide dust, most face powder, most paint pigments | hospital & general surgery |
| 9–12 | 1.0–3.0 μm | Legionella, Humidifier dust, Lead dust, Milled flour, Auto emission particulates, Nebulizer droplets | Superior residential, better commercial, hospital laboratories |
| 5–8 | 3.0–10.0 μm | Mold, spores, dust mite debris, cat and dog dander, hair spray, fabric protector, dusting aids, pudding mix | Better residential, general commercial, industrial workspaces |
| 1–4 | > 10.0 μm | Pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers, carpet fibers | Residential window AC units |