Typical air vs. spike days
- Annual average PM2.5 (8.69 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (100.69 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 Graham without contradicting EPA-aligned thresholds.
Local Pollen and Moisture Load
In Pierce County, the burden on HVAC filters is not just from particulates; it is the heavy seasonal pollen and mold. The damp climate near the Puyallup River valley encourages mold spores to thrive, especially during the transition from wet to dry seasons. Tree pollen in the spring and grass pollen in the summer create a constant influx of biological material into the home. These larger particles do not just affect your breathing; they physically clog filter media, reducing airflow and forcing your blower motor to work harder. If you see a gray or yellow film on your filter after only a month, it is doing its job against the local vegetation load.
Technician Filter Recommendations
Because the city experiences PM2.5 spikes exceeding 100 µg/m³, I recommend a MERV 13 pleated filter for most modern HVAC systems. A MERV 13 is dense enough to capture the fine particulates seen during those peak days without excessively restricting airflow, provided the system is rated for it. If your system is older or has a smaller cabinet, stick with a high-quality MERV 11 and supplement it with a standalone HEPA unit. In this part of Washington, humidity can lead to moisture buildup in the ductwork, so filters should be inspected every 60 days. If the filter looks damp or smells musty, replace it immediately to prevent mold growth. Standard 90-day intervals are often too long during the peak pollen or high-humidity months.