Typical air vs. spike days
- Annual average PM2.5 (8.22 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (28.71 µg/m³) is what filtration must handle during bad-air events.
Sections below reference one or both metrics on purpose — that is how HVAC vs. portable guidance differs for Greer without contradicting EPA-aligned thresholds.
Seasonal Load on HVAC Systems
Pollen and mold are the constant, invisible loads on local HVAC systems. In the Upstate, tree pollen in the spring and ragweed in the fall create a heavy biological burden. Near the Enoree River, humidity levels often climb, which can foster mold growth if indoor moisture isn't managed. These particles are significantly larger than PM2.5 but they clog filters much faster. When a filter is caked with yellow pine dust or mold spores, its airflow drops, forcing the blower motor to work harder and reducing its ability to capture the finer, more dangerous combustion particles. Regular filter replacement is less about the air being dirty and more about maintaining the system's capacity to breathe.
Technician's Filter Recommendations
Because PM2.5 peaks exceed 25 µg/m³, I recommend a MERV 13 pleated filter for most modern HVAC systems. This rating is high enough to capture the fine particles seen during those peak days without being so restrictive that it damages your equipment. If your system is older or has a smaller blower, stick with a MERV 11 and supplement it with a standalone HEPA unit. Given the ozone spikes of 0.0713 ppm, look for filters that include a layer of activated carbon; this is the only effective way to chemically neutralize ozone gas as it passes through the ductwork. In this part of South Carolina, the combination of high humidity and seasonal pollen means you should be swapping these filters every 60 to 90 days. Waiting longer allows biological material to settle on the filter media, which can lead to odors or restricted airflow during the peak cooling season.