Typical air vs. spike days
- Annual average PM2.5 (12.34 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (35.98 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 Granada Hills without contradicting EPA-aligned thresholds.
Mountain Dust and Seasonal Pollen
The proximity to the Santa Susana Mountains introduces a variety of seasonal allergens, including native grasses and mountain mahogany pollen. These particles, along with mold spores that thrive during humid shifts, create a persistent physical load on home air filters. During the transition between seasons, the volume of airborne organic material increases, often leading to a visible buildup on intake vents. Managing this seasonal load is necessary for maintaining proper airflow and ensuring that the HVAC system does not become a source of recirculated allergens.
Technician's Filter Recommendation
For homes in this area, a MERV 13 filter is the professional standard. Since the maximum PM2.5 recorded is 35.98 µg/m³, a lower-rated filter will simply allow too many fine particles to pass through the heat exchanger and back into the living space. Because ozone levels also peak significantly at 0.0917 ppm, a filter with an integrated carbon media is highly effective at neutralizing odors and gaseous irritants. Change these filters every 60 days if you have pets or high foot traffic, and never exceed 90 days. The combination of mountain dust and seasonal pollen can quickly clog a high-efficiency filter, leading to higher energy bills and potential equipment failure if left unchanged.