What does MERV Rating have to do with choosing an air filter?

Written by Garland Heating and Air

What is MERV Rating?

MERV stands for Minimum Efficiency Reporting Value. This is an industry standard rating system that allows you to compare filters made by different manufacturers and this was developed by the Americal Society of Heating, Refrigeration and Air Conditioner Engineers, in short form ASHRAE. This rating is a numerical value ranging from 1 (lowest efficiency) to 20 (highest efficiency) and tells the consumer how well the filter captures and holds dirt and dust of a specified size range. The chart below shows the MERV ratings, corresponding particle size ranges, and efficiency level as measured by the percentage of particles captured. Some of the common particles are pollen, dust mites, mold spores, duat, pet dander, textile fibers, smoke, etc. This scale was designed to show the worst case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers.

MERV Rating

MERV rating chart


You might think that a higher MERV rating would automatically be better, but it’s not. The higher the MERV rating, the smaller the pores are for the air to flow through an HVAC filter. This can create more resistance in airflow than a system is designed to manage, thus making it inefficient. Reducing the air flow in your system can actually worsen the air quality in your home and put a damaging amount of pressure on the fan of your furnace or AC system.

MERV rating standard

MERV 1–4 | 10.0 μm – Pollen, dust mites, cockroach debris, sanding dust, spray paint dust, textile fibers, carpet fibers.

Residential window AC unit.

MERV 5–8 | 10.0–3.0 μm – Mold, spores, dust mite debris, cat and dog dander, hair spray, fabric protector, dusting aids, pudding mix.

Residential, general commercial, industrial workspaces. Can call better condition than before.

MERV 9–12 | 3.0–1.0 μm – Legionella, Humidifier dust, Lead dust, Milled flour, Auto emission particulates, Nebulizer droplets.

Residential, better commercial, hospital laboratories. Better condition.

MERV 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. Its the best rating.

MERV 17–20 | < 0.3 μm – Virus, carbon dust, sea salt.

Smoke electronics & pharmaceutical manufacturing cleanroom. This is a superior condition.

So it is worth doing some research. from the information above we can say the higher ratings mean a greater percentage of particles on each pass. the right MERV rating on the filter can strongly impact the indoor air quality resulting healthy lifestyle. Call your local HVAC expert Garland Heating And Air for the best solutions.

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