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 Brookfield without contradicting EPA-aligned thresholds.
Seasonal Load and Local Factors
Seasonal pollen and mold spores represent a hidden load on your HVAC filters in this region. The proximity to the Fox River corridor and local green spaces contributes to high tree pollen counts in spring and weed pollen in late summer. Humidity levels in Waukesha County also fluctuate, which can lead to mold growth in damp basements or ductwork if not properly managed. These biological particles are often larger than PM2.5 but are produced in massive volumes, meaning they can clog a standard fiberglass filter in a matter of weeks during peak seasons.
Technician's Filter Recommendations
Based on the peak PM2.5 levels exceeding 35 µg/m³, I recommend a MERV 13 pleated filter for most Brookfield homes. A MERV 13 is dense enough to capture the fine combustion particles and smoke that contribute to those worst-day spikes. Because the ozone peaks are also relatively high at 0.0826 ppm, a filter with an activated carbon layer is highly beneficial for neutralizing odors and gaseous pollutants that standard filters miss.
- Filter Grade: MERV 13 for particulate capture.
- Ozone Protection: Activated carbon media.
- Replacement Cycle: Every 60 to 90 days.