Indoor Air Quality
Wildfire smoke, allergies, and tight modern construction make indoor air quality a real concern in California. This page separates what helps from what is marketing, with sources.
Last updated: 2026-09-15
Filtration and MERV ratings
MERV rates how well a filter captures particles. MERV 13 and above capture most smoke and allergy particles. Higher MERV increases airflow resistance, so confirm your system can handle it before upgrading.
Wildfire smoke
During smoke events, upgrade to MERV 13+ (or a HEPA portable air cleaner), seal leaks, and run the system on recirculation. EPA and Cal/OSHA publish guidance on protecting indoor air during wildfires.
Ventilation requirements
New and remodeled California homes must meet Title 24 ventilation requirements (often a whole-house exhaust or supply system) to bring in fresh air without wasting energy.
Humidity, UV, and ionization claims
Maintaining 30–50% relative humidity helps comfort and limits mold. UV systems can reduce microbial growth on coils when correctly sized. Be cautious of broad ionization claims; ask for independent test data.
Duct cleaning
EPA says duct cleaning has not been proven to prevent health problems and is only clearly warranted when ducts are visibly contaminated or after construction/renovation. It is not routine maintenance.
Carbon monoxide and radon
CO detectors are required by California law. Radon is less common but exists in some regions; test kits are inexpensive. Both are safety issues, not comfort issues.
Homeowner checklist
- Confirm your system can handle MERV 13+ airflow
- Run recirculation and portables during smoke events
- Maintain 30–50% indoor humidity
- Install and test CO detectors
- Ask for independent data before buying UV or ionization