Why it matters to you
Charleston's heavy spring pine and oak pollen loads filters fast, and pollen grains are large enough that mid-range filters catch them well. Many older Lowcountry systems with small returns cannot push air through high-MERV filters, which cuts cooling, dehumidification, and coil protection.
Practical guidance
Choose the filter your system was designed for, not the highest number on the shelf, and inspect it monthly during pollen season. If you want high-efficiency filtration your filter slot cannot support, ask about a media cabinet or a dedicated air cleaner.
MERV tiers and what they typically capture (ASHRAE 52.2)
| MERV range | Typical particles captured | Where it fits |
|---|---|---|
| MERV 1–4 | Large particles: pollen, dust mites, sanding dust, carpet fibers | Basic equipment protection; minimal air cleaning |
| MERV 5–8 | Mold spores, pet dander, finer household dust | Common residential choice; good pollen capture with modest resistance |
| MERV 9–12 | Finer dust, lead dust, auto emissions, humidifier dust | Better residential filtration if the return and blower can handle it |
| MERV 13–16 | Bacteria, smoke, sneeze droplets, very fine particles | High-efficiency filtration; can restrict airflow on systems not designed for it — often needs a media cabinet or larger return |
