Typical air vs. spike days
- Annual average PM2.5 (8.03 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (36.03 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 Boerne without contradicting EPA-aligned thresholds.
Seasonal Load and Local Factors
Pollen and mold are the constant, invisible loads on your HVAC system in the Hill Country. Residents near the Cibolo Creek area often deal with higher humidity levels that can contribute to mold spores. Seasonal spikes from Mountain Cedar in the winter and Oak in the spring create a thick layer of biological dust. This debris accumulates on your evaporator coils and inside ductwork if your filter is not tight enough. These regional allergens often cause more daily indoor air quality complaints than industrial pollutants, as they physically clog filters and reduce the efficiency of your cooling system during the hottest months.
Technician's Filter Recommendation
Because PM2.5 peaks exceed 25 µg/m³, I recommend a MERV 13 pleated filter for most modern systems. This rating is high enough to capture the fine combustion particles and smoke that characterize those worst-day spikes. Since ozone peaks reach 0.08 ppm, look for a filter with an integrated activated carbon layer to help neutralize gases. In this part of Texas, the combination of high pollen counts and humidity means you should follow a strict maintenance schedule:
- Change filters every 60-90 days: Do not wait for the filter to look black; the fine particles that restrict airflow are often invisible.
- Check seals: Ensure the filter fits tightly in the rack to prevent air bypass.
- Bedroom HEPA: Supplement your HVAC with a standalone HEPA unit if anyone in the home has asthma.
Waiting too long to change a high-MERV filter can strain your blower motor and reduce cooling efficiency, especially during a Texas summer.