Typical air vs. spike days
- Annual average PM2.5 (8.40 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (26.24 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 Decatur without contradicting EPA-aligned thresholds.
Seasonal Load and Local Environment
Residents deal with heavy seasonal loads from the dense urban forest and nearby parks. Pine and oak pollen are the primary culprits, often coating outdoor surfaces and being pulled into the HVAC return air. High humidity levels in the area also promote mold growth within ductwork and on damp filters. This organic debris doesn't just sit there; it breaks down and can be recirculated if the filtration system isn't maintained. The local humidity makes filter management a year-round priority to prevent biological growth.
Technician's Filter Recommendation
I suggest using a MERV 13 filter to handle the PM2.5 spikes that exceed 25 µg/m³. This level of filtration is necessary to trap the microscopic particles that standard fiberglass filters miss. Given the ozone peaks of 0.0813 ppm, a filter with integrated charcoal or carbon is highly effective at reducing chemical smells and gaseous pollutants. Change these filters every 2 to 3 months. In Decatur, if you have pets or a high-traffic household, you should lean toward the 60-day mark to prevent the HVAC system from choking on accumulated dust, dander, and seasonal pollen.