Typical air vs. spike days
- Annual average PM2.5 (8.89 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (42.26 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 Davis without contradicting EPA-aligned thresholds.
Agricultural and Regional Load
The area surrounding the city is heavily influenced by Central Valley agriculture and the Putah Creek riparian zone. This results in a high seasonal load of pollen, dust, and organic matter. These larger particles act as carriers for smaller pollutants, creating a thick layer of debris on HVAC coils if the filter is bypassed. During harvest seasons or high-wind events, the volume of airborne material increases significantly. This local dust is often fine and alkaline, which can be abrasive to HVAC components if the system is not properly sealed and filtered.
Technician's Filter Recommendations
Given the PM2.5 peaks exceeding 40 µg/m³, I recommend a MERV 13 pleated filter as the minimum standard for Davis homes. Anything lower will allow fine particulates to cycle through your living space. Because ozone levels reach 0.073 ppm, I also suggest using a filter that incorporates activated carbon. Carbon is the only effective way to pull ozone and odors out of the air stream. Due to the heavy dust and agricultural load, change your filters every 60 days. Waiting 90 days in this region often leads to restricted airflow, which increases utility bills and puts unnecessary strain on your blower motor. A clean MERV 13 filter is your best defense against the Central Valley's toughest air days.