Indoor air quality and filtration in Austin, TX.

Air quality in Central Texas has a calendar. Mountain cedar releases from roughly December through February and produces the reaction people here call cedar fever, which is severe enough that it drives clinic visits across the region. Oak follows in spring and coats everything in yellow. Between and around them there is dust — from caliche roads, from construction, from a landscape that is dry for long stretches. All of it ends up wherever the house is pulling air from.

That is the part most people miss: filtration only cleans the air the system actually pulls through the filter. If the return plenum, the return chase or the filter grille leaks — and in a lot of houses here they do — the system is drawing unfiltered attic and wall-cavity air straight past the filter and distributing it. Sealing the return side is often a bigger air quality improvement than upgrading the filter, and it costs less.

Then there is filter selection, which involves a genuine trade-off. A denser filter catches more and restricts more, and a system already fighting high static pressure will lose airflow, run a colder coil and perform worse. The right answer is a filter matched to the system's capability, in a big enough filter area to keep the pressure drop reasonable — sometimes that means a media cabinet rather than a thicker one-inch filter. Humidity is the other half: this is not a dry climate, and a system that short-cycles never runs long enough to dehumidify, which is why some houses read 72 degrees and still feel damp.