Typical air vs. spike days
- Annual average PM2.5 (8.39 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (34.80 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 Woodland without contradicting EPA-aligned thresholds.
Local Pollen and Dust Loads
Woodland sits in an agricultural region where seasonal shifts bring heavy pollen and dust loads. The Yolo County landscape contributes significant oak and grass pollen in the spring, followed by harvest dust later in the year. These larger particles do not always show up in PM2.5 data, but they clog HVAC filters quickly. If you notice a drop in airflow or more dust on your surfaces, it is usually the seasonal biological load rather than fine chemical smoke. Keeping the filtration system clean during these transitions prevents the blower motor from overworking and maintains indoor air velocity.
Technician Filter Recommendations
Because PM2.5 peaks exceed 25 µg/m³, I recommend a MERV 13 filter for your central system. A standard MERV 8 will not catch the fine particles seen during those 34.8 µg/m³ spikes. Since ozone also hits 0.0732 ppm, look for a filter with an activated carbon layer to help neutralize odors and gases. In this part of California, filters should be swapped every 60 to 90 days. If you live near active farmland or construction, check the filter every 30 days. A MERV 13 provides the right balance of filtration without putting too much static pressure on most modern blowers. If your system is older, a MERV 11 paired with a standalone HEPA unit is a safer alternative to avoid stressing the motor.