Typical air vs. spike days
- Annual average PM2.5 (9.11 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (38.18 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 Granite City without contradicting EPA-aligned thresholds.
Seasonal Load and Humidity
Being near the Mississippi River means dealing with high humidity and the resulting mold spores. Seasonal pollen cycles are intense, with ragweed and oak being major contributors to the local dust load. These particles are heavy and sticky, often coating the cooling coils of your HVAC system if the filter isn't up to the task. This buildup doesn't just hurt air quality; it forces the system to run longer and harder, increasing your utility bills and shortening the lifespan of the equipment. Regular filter changes are necessary to manage this heavy biological load.
HVAC Filter Recommendations
Since PM2.5 peaks exceed 25 µg/m³, I strongly recommend a MERV 13 pleated filter for Granite City homes. This level of filtration is necessary to capture the fine particulates seen during those 38.18 µg/m³ spikes. Additionally, because ozone levels hit 0.0771 ppm, look for filters that incorporate activated carbon to scrub odors and gases. Change your filters every 60 days during peak summer and winter months. If you notice a grey film on your registers, it is a sign your current filter is bypassing or overloaded. A MERV 13 provides the best balance of protection and airflow for this specific environment, ensuring your HVAC system doesn't become a source of indoor pollution.