Typical air vs. spike days
- Annual average PM2.5 (8.03 µg/m³) reflects usual daily exposure.
- Worst-day peak PM2.5 (41.51 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 Galveston without contradicting EPA-aligned thresholds.
Coastal Humidity and Biological Load
Humidity and coastal winds define the local environment. Mold spores are a constant presence given the proximity to the Gulf of Mexico, often spiking after heavy rain or during humid summer months. Pollen from ragweed and oak also adds a heavy biological load to home filtration systems. In the city, these allergens do not just stay outside; they accumulate in ductwork and on evaporator coils, reducing system efficiency and recirculating through the house. The salt-heavy air can also interact with indoor dust, making it more likely to settle on surfaces and inside HVAC components.
Technician's Filter Recommendation
Because PM2.5 peaks in Galveston exceed 40 µg/m³, a MERV 13 filter is the professional recommendation for your central HVAC system. This grade is dense enough to capture the fine combustion particles and smoke that characterize peak pollution days. Since ozone levels also spike significantly, look for a filter with an activated carbon layer to help neutralize gaseous pollutants. In this humid coastal climate, change your filters every 60 days. High moisture levels can cause dust to cake on the filter media, restricting airflow and putting unnecessary strain on your blower motor. A standard MERV 8 or fiberglass filter is insufficient for the particulate spikes documented here.