Typical air vs. spike days
- Annual average PM2.5 (8.83 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (32.44 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 Algonquin without contradicting EPA-aligned thresholds.
Local Environmental Loads
The Fox River corridor brings specific challenges for filtration in the area. Seasonal transitions trigger heavy pollen releases from oak and maple trees, followed by high mold spore counts during humid summer months. These biological loads act as a pre-filter on your HVAC system, clogging media and reducing airflow before fine dust even hits the surface. Residents often notice a grey or yellow film on outdoor surfaces during peak pollen season; that same material is being pulled into your return air vents and settling on your AC coils.
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 dense enough to capture the fine soot and smoke particles that characterize those 32.44 µg/m³ spike days. Given the ozone peaks of 0.0819 ppm, look for a filter with an activated carbon layer to help neutralize gaseous pollutants and odors. In this part of Illinois, humidity and seasonal pollen mean you should swap your filter every 60 to 90 days. Do not wait for the filter to look completely black; a greyish hue already indicates a significant pressure drop that can strain your blower motor and increase energy costs. If you have pets, check the filter every 30 days.