Typical air vs. spike days
- Annual average PM2.5 (8.77 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (25.78 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 Desoto without contradicting EPA-aligned thresholds.
Regional Pollen and Mold Load
In this part of Dallas County, the seasonal pollen load is the main threat to indoor air quality and HVAC efficiency. The proximity to local parks and greenbelts means oak, elm, and cedar pollen are heavy contributors to the dust found inside homes. Mold spores also become a factor during the humid transition months. These allergens act as a pre-filter on your HVAC system, often clogging the pleats of a standard filter before the fine particulates even have a chance to get caught. This biological load requires more frequent filter changes than the air quality data alone might suggest.
Technician's Filter Recommendations
I recommend a MERV 13 pleated filter for homes in the area. The peak PM2.5 of 25.78 µg/m³ is high enough that a standard MERV 8 or 11 will let too many fine particles through. If you have a sensitive respiratory system, look for a filter that includes a carbon or charcoal layer to address the ozone spikes that reach 0.0768 ppm.
- Filter Grade: MERV 13 to capture fine particulates during spikes.
- Ozone Protection: Activated carbon layer is highly recommended.
- Change Frequency: Every 60 days during peak cooling season.
- Maintenance: Ensure the filter rack has a tight seal to prevent bypass.
The combination of Texas heat and high humidity can cause captured organic material like pollen to break down, which can lead to musty odors if the filter is left in place for too long. Change these filters every 60 days to maintain airflow and air quality.