Typical air vs. spike days
- Annual average PM2.5 (9.78 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (26.25 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 Alton without contradicting EPA-aligned thresholds.
Seasonal Loads and River Humidity
Proximity to the Mississippi River creates a specific set of challenges for Alton HVAC systems. High humidity levels during the summer months promote mold spore growth, which adds a heavy biological load to your air filters. Spring and fall bring heavy tree and ragweed pollen, which can quickly clog a filter and reduce system airflow. This seasonal debris doesn't just affect your breathing; it forces your blower motor to work harder, increasing energy costs and wear on the equipment. Keeping an eye on the filter's physical condition during these transitions is more effective than following a generic calendar reminder.
Technician's Filter Recommendations
Based on the peak PM2.5 levels exceeding 25 µg/m³ and ozone spikes reaching 0.0761 ppm, I recommend a MERV 13 pleated filter for most the city homes. A MERV 13 is dense enough to capture the fine combustion particles and smoke that make up PM2.5 spikes without severely restricting airflow in modern systems. Because ozone levels also peak significantly, look for a filter that includes an activated carbon layer. Carbon is the only effective way to neutralize ozone and odors as they pass through the ductwork.
- Change Frequency: Every 60 to 90 days. If you live near the river or have pets, check it at the 45-day mark.
- Secondary Protection: Use a standalone HEPA unit in primary living areas during peak ozone days.
- System Check: Ensure your HVAC cabinet is sealed tightly; a high-MERV filter is useless if air leaks in around the frame.