Typical air vs. spike days
- Annual average PM2.5 (8.66 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (101.91 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 Tacoma without contradicting EPA-aligned thresholds.
Pollen and Mold Loads
Pollen and mold are the constant, invisible loads on your HVAC system. In the Puget Sound region, tree pollen from alder and birch starts early, followed by heavy grass seasons. Mold spores thrive in the damp climate, especially near the Port of Tacoma and surrounding low-lying areas. These biological particles accumulate on your evaporator coils and inside ductwork if your filter is not seated correctly. This buildup reduces airflow and forces the blower motor to run longer, increasing your utility bills and wear on the equipment. A high-quality pleated filter captures these larger biological particles before they can settle into the mechanical components of your furnace or heat pump.
Technician Filter Recommendations
Because Tacoma sees PM2.5 spikes well over 25 µg/m³, I recommend a MERV 13 pleated filter for your central system. A MERV 8 or 11 is insufficient when outdoor air hits the levels seen on the worst days here. MERV 13 is dense enough to capture the fine soot and smoke particles that characterize these spikes. Consider these maintenance steps:
- Change filters every 60 days: The combination of high particulate events and local humidity can lead to filter loading faster than the standard 90-day recommendation.
- Check the seal: Ensure there are no gaps around the filter frame where air can bypass the media.
- Supplement with HEPA: If your HVAC cabinet cannot handle the static pressure of a MERV 13, stick with a MERV 11 and supplement with a standalone HEPA unit in high-traffic rooms.