Radon: test the home you live in
The California Department of Public Health encourages all Californians to test their homes for radon, and EPA says its radon zone map shouldn't be used to decide whether an individual home needs testing. Test anyway, EPA says, and fix the home if the level is 4 picocuries per liter or higher.
The California Geological Survey's Special Report 247 (2022) and an interactive California Radon Potential Map cover the whole state.
What a whole-house air purifier costs in California
We estimate $395 to $5,350 per installed system for this job in California. That's a model, not a quote: one national published cost range, widened by 15 percent each side and adjusted by California's wage ratio to the US (1.16).
A whole-house air purifier is estimated at $395 to $5,350 per installed system. That's wide, because it rests on one national range, widened 15 percent each side and adjusted by California's technician wage ratio of 1.16. It's an estimate, not a quote, so ask what each item on the bid does.
| Item | Figure | What it is |
|---|---|---|
| Estimated range, not a quote | $395 to $5,350 per installed system | Built from one national published range, adjusted by the California HVAC technician wage ratio (1.16). California company prices are shown separately. Basis: no state company sample (no counted California company price for this job), national estimate only. |
| Technician wage, California mean | $36.24 an hour | Pay per BLS for May 2025; what the technician earns, not the price of the job. |
How we estimate costs: the Estimated range row is a model, not a quote. We have no counted California company price for this job, so the range is our national estimate alone. Our national estimate takes one published national range for this job (a cost guide from a third-party site that we have not verified and do not cite) and multiplies it by California's HVAC technician wage ratio to the US (1.16, BLS OEWS May 2025, heating, air conditioning and refrigeration mechanics and installers). The wage and permit rows below are what HVAC technicians are paid and what a city charges, and neither is a price. We have not collected quotes. Full method. Prices as of Oct 23, 2026.
Carbon monoxide from gas appliances
SoCalGas explains that carbon monoxide can build up when gas appliances aren't working properly or combustion gases aren't vented safely. SDG&E advises a detector on each floor. If one sounds, SoCalGas says to evacuate, keep everyone out until it's safe and call 911; SDG&E says not to use the appliance until a qualified, licensed professional confirms it's safe.
Filters, ducts and ventilation
CSLB's C-20 text puts the ducts, registers, flues and air filters of a heating or air-conditioning system inside licensed work. The CEC says the 2025 Energy Code, which applies to permit applications from January 1, 2026, strengthens ventilation standards. For the permit and HERS rules on duct changes, see duct cleaning.
Purifiers and UV lamps
None of the California or federal pages we cite rates air purifiers or UV lamps. A company that sells one should show you the source for its claim and tell you what it costs to run. Ask for the license number too.
Indoor air problems that need action today
- A carbon monoxide alarm is sounding: get outside, call 911 and stay out until it's cleared.
- You smell gas: leave, then call 911 and your gas utility.
- Someone indoors has sudden flu-like symptoms, headaches, nausea or drowsiness: get everyone out and call 911.
- You're curious about radon: order a test kit and follow EPA's action level.
- Dust is the only complaint.
Low-cost steps with a source
- Test for radon; EPA says to fix at 4 picocuries per liter or higher.
- Put a carbon monoxide detector on each floor.
- Replace the furnace or AC filter when it's clogged.
Permits for indoor air work
Swapping a filter or running a radon test isn't on CSLB's permit list. Replacing the air handler or coil, or adding ducting, is, according to its letter to C-20 contractors. Your building department decides anything in between.
Before any work starts, get the license number and check it with your state's licensing board; our state pages link the lookup.
Questions people ask
Should I test my California home for radon?
Yes; the state health department encourages all Californians to test. EPA's map shouldn't be used to decide whether a particular home needs a test. Fix the home if the result is 4 picocuries per liter or higher.
Where should carbon monoxide detectors go?
SDG&E advises one on each floor. If an alarm sounds, evacuate and call 911. SoCalGas lists sudden flu-like symptoms, headaches, nausea and drowsiness as signs.
What does a whole-house air purifier cost in California?
The model gives $395 to $5,350 per installed system for an installed system; it is an estimate, not a quote. The range is wide because the one national range behind it is. No California company price for this work is in our count yet.
Who may work on the ducts and filters?
A C-20 contractor, with a narrow exemption for casual work under $1,000 that needs no permit. B&P 7048 sets the exemption, and anyone who advertises as a contractor or hires help loses it.
- U.S. Bureau of Labor Statistics, OEWS May 2025: Heating, Air Conditioning, and Refrigeration Mechanics and Installers (SOC 49-9021), California, mean hourly wage Read Oct 23, 2026.
- EPA: The EPA Map of Radon Zones Read Oct 20, 2026.
- CDPH: Radon Read Oct 20, 2026.
- Carbon Monoxide | SoCalGas Read Oct 20, 2026.
- Carbon monoxide | San Diego Gas & Electric Read Oct 20, 2026.
- Emergency Information | SoCalGas Read Oct 20, 2026.
- Gas Safety | PG&E Read Oct 20, 2026.
- Gas safety | San Diego Gas & Electric Read Oct 20, 2026.
- CSLB: Licensing Classifications Detail, C-20 Read Oct 20, 2026.
- California Legislative Information: BPC 7048 Read Oct 20, 2026.
- CEC: 2025 Building Energy Efficiency Standards Read Oct 20, 2026.
- CSLB: C-20 Permit Enforcement Letter (PDF, 2010) Read Oct 20, 2026.
- HVACMatch: how we estimate costs, California (editorial policy) Read Oct 23, 2026.