Typical air vs. spike days
- Annual average PM2.5 (8.88 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (37.16 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 Saratoga without contradicting EPA-aligned thresholds.
Regional Pollen and Mold Load
Seasonal allergens act as a heavy physical load on your home's filtration system. In the foothills near the Santa Cruz Mountains, oak and redwood pollen are major contributors to filter clogging during the spring months. As the area transitions from damp winters to dry summers, mold spores also become a factor in the local air. These biological particles are significantly larger than PM2.5 but are responsible for the visible grey or yellow buildup on your HVAC filter. High humidity periods can also cause these trapped organic materials to break down, potentially impacting indoor air if the filter is not replaced regularly.
HVAC Filter Recommendations
Because peak PM2.5 levels in the city exceed 25 µg/m³, I recommend using a MERV 13 pleated filter. A MERV 13 is the minimum grade required to effectively capture the fine particulates found during those 37.16 µg/m³ spikes. Standard MERV 8 filters are designed to protect the HVAC equipment from large dust, but they allow fine smoke and exhaust particles to pass through. Given that ozone peaks reach 0.0795 ppm, you should also consider a filter with an activated carbon layer to help neutralize gaseous irritants. In local homes, filters should be checked every 30 days and replaced every 60 to 90 days. If you notice the filter media is dark or starting to bow, it is a sign of high static pressure, which can strain your blower motor and increase energy costs.