Typical air vs. spike days
- Annual average PM2.5 (8.81 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (36.36 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 Pekin without contradicting EPA-aligned thresholds.
Seasonal Load and the Illinois River
Seasonal shifts in the Illinois River valley bring a heavy load of organic material into the air. Spring tree pollen and fall mold spores act as a constant physical tax on your HVAC system. These particles are much larger than PM2.5 but are produced in massive volumes, often clogging filters faster than expected. If you notice a gray or yellow film on your registers, your filter has likely reached its holding capacity. High humidity in the summer can also lead to moisture retention in filter media, which restricts airflow and can lead to musty odors if the filter isn't swapped out regularly. Keeping a fresh filter during the transition between heating and cooling seasons is the best way to manage this biological load.
Technician's Filter Recommendations
Based on a maximum PM2.5 of 36.36 µg/m³, I recommend a MERV 13 pleated filter for Pekin homes. This rating is high enough to capture the fine combustion particles and smoke that characterize peak pollution days. If your HVAC system is older and struggles with the static pressure of a MERV 13, drop to a MERV 11 but ensure it is changed every 60 days. Because the ozone peaks reach 0.0691 ppm, filters with an activated carbon layer are beneficial for neutralizing odors and gases that standard dust filters miss. Change your filters at the start of the heating and cooling seasons at a minimum, though a 90-day cycle is the maximum I suggest for maintaining airflow and air purity. In households with pets or high traffic, a 60-day replacement cycle is better to prevent the filter from becoming a source of dust itself.