Minimum Efficiency Reporting Value

"MERV" Ratings

What is MERV? MERV stands for Minimum Efficiency Reporting Value. It is a number from a test method designed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). The number is intended to help people compare filters. Generally speaking, a higher MERV rating indicates better filter performance.



MERV Value

Average Particle Size Efficiency

(0.3-1 Microns)

Average Particle Size Efficiency

(1-3.Microns)

Average Particle Size Efficiency

(3-10 Microns)

Particles that are trapped:

MERV 1

-

-

Less than 20%

Pollen, Dust Mites, Standing Dust, Spray Paint Dust, Carpet Fibers.

MERV 2

-

-

Less than 20%

MERV 3

-

-

Less than 20%

MERV 4

-

-

Less than 20%

MERV 5

-

-

20%-34%

All of the above and Mold Spores, Hair Spray, Fabric Protector, Cement Dust.

MERV 6

-

-

35%-49%

MERV 7

-

-

50%-69%

MERV 8

-

-

70%-85%

MERV 9

-

Less than 50%

85% or better

All of the above and Humidifier Dust, Lead Dust, Auto Emissions, Milled Flour.

MERV 10

-

50%-64%

85% or better

MERV 11

-

65%-79%

85% or better

MERV 12

-

80%-89%

90% or better

MERV 13

Less than 75%

90% or better

90% or better

All of the above and Bacteria, Most Tobacco, Smoke, etc.



Particles and Their Micron Ratings

(a micron is a unit of measurement in the metric system equal to 1 millionth of a meter in length)


Particle

Approximate Particle Size

(microns)

Bacteria

0.2-1

Dust Mites

3

Hair Spray

10

Human Hair

100

Pollen

10

Mold Spores

3

Tobacco Smoke

1