Indoor air quality work in Sunnyvale, Santa Clara and Cupertino starts with one question: what are you trying to fix? Wildfire smoke, household dust, allergy symptoms, cooking or pet odors, dry winter air, damp rooms and stuffy bedrooms each need a different answer. Which answer works depends on the filter rating your system can carry, blower capacity, duct leakage, ventilation and humidity. That is why the HVAC system gets checked before anyone recommends equipment.
Match the problem to the fix
| Problem | What usually helps | More detail |
|---|---|---|
| Wildfire smoke | MERV 13 media filter, fan circulation, sealed return ducts, portable HEPA in bedrooms | Wildfire smoke filtration |
| Dust | A filter that fits its slot, sealed returns, cleaning ducts that are actually dirty | Duct cleaning |
| Allergies | Finer filtration and humidity in range | Allergy relief |
| Odors, stale air | Fresh-air ventilation | Ventilation systems |
| Dry winter air | Whole-home humidifier | Humidifier installation |
| Damp rooms, condensation | Dehumidification and ventilation | Dehumidifier installation |
| Musty coil or drain pan | UV light at the indoor coil | UV light air treatment |
For filtration equipment, see air filtration systems and air purifier installation.
Wildfire smoke days and filtration
Late summer and fall can bring smoke days, and smoke is made of very fine particles that a basic fiberglass filter mostly lets through. A MERV 13 filter catches a large share of them. Higher MERV numbers capture finer particles, but they also resist airflow more, and a dense filter crammed into a 1-inch slot can starve the blower: weak airflow, a frozen AC coil in summer, a furnace tripping its high limit in winter. A 4- or 5-inch media cabinet gives the same filtration with far more surface area and less resistance.
On smoke days, close windows, set the thermostat fan to On so air keeps passing through the filter, and check the filter once the smoke clears. Leaks in the return duct between the filter and the blower pull in unfiltered attic or crawlspace air, so sealing them matters as much as the filter itself. Sensitivity also varies by room: someone with asthma may need a portable HEPA unit in the bedroom on top of whole-home filtration. Our article on indoor air during wildfire smoke has more.
Blower capacity and static pressure
Every filter adds resistance, and the blower can only push against so much. Before upgrading, we measure total static pressure and compare it with the blower’s rating. Older fixed-speed blowers simply lose airflow as resistance rises. Variable-speed blowers ramp up to hold airflow, which costs more power and noise. Many older homes have a single small return grille; adding a return or a larger filter grille is often what makes better filtration possible.
Sensi air purifier or a portable unit?
If you are comparing a Sensi air purifier or any other portable purifier with whole-home filtration, check four things: room coverage (the clean air delivery rate against your room size), filter replacement cost over a year, noise on the setting you will actually use, and HVAC airflow. A portable unit does not touch your HVAC airflow; a whole-home filter does. Portable units clean one room around the clock; whole-home filtration cleans every room the ducts reach, but only while the fan runs. Avoid ozone-generating “purifiers” in either form, since ozone irritates the lungs. For thermostats, see our Sensi page.
Whole-home checks before adding filtration
- Static pressure with the current filter, and the risk a denser filter adds.
- Return size and filter location.
- Duct leakage, especially on the return side.
- Ventilation: whether the home gets fresh air beyond leaks around doors and windows.
- Humidity, ideally around 30 to 50 percent.
- Whether the existing furnace or air handler can support the upgrade at all.
An air quality check ends with these findings, the options and the cost factors, before any equipment is installed.
Local notes
Smoke days usually arrive in late summer and fall, so the time to upgrade filtration is before then. Eichler homes heated through the slab have no ducted system to filter, so portable purifiers and the filters in ductless heads do the work there; mini-split filters catch dust but are not fine-particle filters. Condos often have a small filter slot in a compact closet, which limits the options. City pages: Sunnyvale, Santa Clara and Cupertino.