A MERV rating (Minimum Efficiency Reporting Value) is the ASHRAE Standard 52.2 score, from 1 to 16, for how well an air filter captures airborne particles between 0.3 and 10 microns. Higher numbers trap smaller particles such as fine dust, pet dander and some smoke, but denser filters can restrict airflow in systems not designed for them.
Why it matters to you
Filtration affects the equipment as well as the air: a filter that is clogged or too restrictive can freeze an evaporator coil, overheat a furnace and strain the blower motor.
Practical guidance
Use the filter size and highest MERV the equipment manufacturer allows; MERV 8 to 11 suits most homes, and MERV 13 is worth discussing with a pro if allergies or smoke are a concern. Check the filter monthly and replace it every one to three months.
Common MERV ratings under ASHRAE Standard 52.2
| MERV | 0.3–1 micron (E1) | 1–3 microns (E2) | 3–10 microns (E3) | Typical home use |
|---|---|---|---|---|
| MERV 8 | Not rated | 20% or more | 70% or more | Standard pleated filter; a sound baseline for most systems |
| MERV 11 | 20% or more | 65% or more | 85% or more | Better capture of fine dust and pet dander; most systems handle it |
| MERV 13 | 50% or more | 85% or more | 90% or more | Fine particles and some smoke; confirm the system's airflow allows it |
| MERV 16 | 95% or more | 95% or more | 95% or more | Hospital-grade; rarely suitable for standard home systems |