Typical air vs. spike days
- Annual average PM2.5 (8.09 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (35.27 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 Franklin without contradicting EPA-aligned thresholds.
Seasonal Load and Lake Michigan
Seasonal allergens in the area are driven by ragweed and grass pollens. The proximity to Lake Michigan can influence local humidity levels, which affects how long mold spores and dust mites remain active in your home. These biological loads accumulate on your HVAC filter, eventually restricting airflow and reducing the system's efficiency. During the spring and fall, the filter acts as the first line of defense against outdoor allergens being pulled into the house. In Franklin, the combination of lake-influenced humidity and high pollen counts means filters can clog faster than in drier climates, requiring more frequent inspections.
Technician's Filter Recommendation
Given the PM2.5 spikes exceeding 35 µg/m³, I recommend a MERV 13 filter for homes in the area. This rating is effective at capturing the fine particles that make up those peak readings. Because ozone also hits high levels of 0.0842 ppm, a filter with an activated carbon layer is a smart addition to help neutralize gases and odors.
- Standard Baseline: MERV 11 is the minimum, but MERV 13 is preferred for the 11.8% of residents with asthma.
- Change Frequency: Replace filters every 60 to 90 days. If you notice a heavy dust load or have pets, stick to the 60-day mark.
- System Check: Ensure your HVAC blower can handle a MERV 13 filter; if the filter looks bowed or sucked in, you may need a professional to adjust the fan speed or use a high-flow pleated version.