Service
Radon Testing in San Diego County
Measurement first. Short-term screening, long-term averages, and continuous monitoring that show what a home is actually breathing.
Every decision about radon starts with a number. Testing is the only way to produce that number, and the quality of the test determines whether the number means anything. A device left on a windowsill next to an open patio door will read low no matter what the soil is doing underneath.
There are three broad approaches. Short-term tests run two to seven days and answer the question of whether a problem may exist. Long-term tests run 90 days or more and produce the annual average that best represents real exposure. Continuous radon monitors log hourly values, which reveals patterns that a single averaged result hides entirely.
Which one is right depends on the reason for testing. A homeowner with time should favor a long-term average. A seller under contract needs a defensible short-term result. A household troubleshooting an existing system needs hourly data.
Why this work matters
- Radon cannot be detected by smell, sight, or symptom, so measurement is the only diagnostic tool available.
- Levels vary house to house on the same street. A neighbor's low reading says nothing reliable about the home next door.
- Results drive money decisions. Mitigating without a valid baseline means never knowing whether the work succeeded.
- Real estate contracts, lending conditions, and disclosure obligations all rest on documented measurements rather than assumptions.
Signs this service applies to your building
- The home has never been tested, which describes the large majority of California houses.
- A below-grade or partially below-grade room is used as living space.
- The last test is more than two years old.
- The home was recently weatherized, re-roofed, or had HVAC replaced.
- A significant renovation opened or resealed the slab.
- A purchase or sale is underway and a documented result is needed.
How the process works
- 1
Establish closed-house conditions
Windows and exterior doors stay closed except for normal entry and exit, beginning 12 hours before a short-term test and continuing throughout. Whole-house fans and window air conditioners stay off.
- 2
Place the device correctly
The detector sits in the lowest level regularly occupied, two to six feet above the floor, at least three feet from exterior walls and windows, and away from drafts, heat, and high humidity.
- 3
Run the measurement period
Short-term devices run 48 hours minimum. Continuous monitors typically run 48 to 96 hours and log each hour. Long-term alpha track detectors stay in place for 90 days to a full year.
- 4
Analyze and report
Continuous monitors produce an on-site report with hourly data, average, and closed-condition compliance. Passive devices are sealed and returned to a laboratory for analysis.
- 5
Interpret and plan
Results at or above 4.0 pCi/L call for mitigation. Results between 2.0 and 4.0 pCi/L warrant serious consideration. Below 2.0 pCi/L, retesting every two years is the sensible cadence.
Equipment and materials involved
Continuous radon monitor
Electronic instrument logging hourly concentrations plus temperature, humidity, and tamper events.
Alpha track detector
Passive long-term device that records cumulative exposure over 90 days to a year.
Charcoal canister
Short-term passive device analyzed by an accredited laboratory.
Liquid scintillation vials
Alternative short-term passive method with laboratory analysis.
Data logger placement kit
Stands and tamper documentation used to keep placement compliant during real estate tests.
What you get out of it
- A defensible, documented number instead of guesswork.
- Hourly data that reveals whether spikes are weather-driven or constant.
- A baseline that makes post-mitigation verification meaningful.
- Peace of mind for households with children, older adults, or anyone spending long hours at home.
- Documentation that supports disclosure during a sale.
San Diego County considerations
The San Diego climate works against casual testing. Homes here are ventilated naturally for much of the year, so a test taken with the sliders open will understate the true closed-condition average.
Seasonal shifts matter. Onshore flow, marine layer, and winter rain all change soil moisture and pressure, and radon entry usually rises when saturated soil caps the ground and forces gas toward the building.
Inland communities on decomposed granite and homes near fractured bedrock in the foothills tend to produce more variable results than coastal sand terraces, which strengthens the case for continuous monitoring over a single passive device.
Because county-wide averages are low, some homeowners assume testing is unnecessary. Averages describe regions, not houses, and elevated homes exist throughout the county.
Frequently asked questions
How long does a radon test take?+
A short-term test needs a minimum of 48 hours of closed-house conditions, and a continuous monitor is typically left for 48 to 96 hours to capture at least two full day-night cycles. Long-term alpha track testing runs 90 days at minimum, and a full year produces the most representative annual average. For a real estate transaction the 48-hour continuous monitor test is standard because it produces a documented, tamper-aware result inside a typical inspection window.
Where should the detector be placed?+
In the lowest level of the home that is used regularly, which in most San Diego houses means the main floor rather than a basement. The device sits two to six feet off the floor, at least three feet from exterior walls, windows, and doors, and at least twenty inches from the floor. It should be away from HVAC supply registers, fireplaces, kitchens, bathrooms, and direct sunlight, all of which distort readings.
Are hardware store test kits reliable?+
Consumer kits from reputable manufacturers give useful screening information when the instructions are followed exactly, particularly the closed-house requirement. Their weaknesses are the absence of hourly data, no tamper detection, and reliance on the occupant to maintain conditions honestly. They are a reasonable first step for a curious homeowner and are not appropriate as the basis of a real estate negotiation.
What time of year is best to test?+
Winter generally produces the highest readings because homes are closed up more and wet soil pushes gas toward the foundation. That said, a test any time of year is far better than no test. If a warm-season short-term test comes back near the action level, following up with a winter or long-term test gives a truer picture of annual exposure.
How often should a home be retested?+
Every two years is a reasonable baseline for a home with a low prior result. Retest sooner after significant renovation, foundation work, HVAC replacement, window replacement, or converting a below-grade space to living area. Homes with a mitigation system should be retested every two years and immediately after any fan replacement.
Related reading
Related services
Available throughout the county
- Radon Testing in San Diego
- Radon Testing in La Jolla
- Radon Testing in Del Mar
- Radon Testing in Carlsbad
- Radon Testing in Encinitas
- Radon Testing in Poway
- Radon Testing in Escondido
- Radon Testing in Chula Vista
- Radon Testing in El Cajon
- Radon Testing in La Mesa
- Radon Testing in Santee
- Radon Testing in National City
- Radon Testing in Coronado
- Radon Testing in Imperial Beach
- Radon Testing in Pacific Beach
- Radon Testing in Mission Valley
- Radon Testing in Clairemont
- Radon Testing in Mira Mesa
- Radon Testing in Rancho Bernardo
- Radon Testing in Rancho Peñasquitos
- Radon Testing in Carmel Valley
- Radon Testing in University City
- Radon Testing in Point Loma
- Radon Testing in Hillcrest
- Radon Testing in North Park
- Radon Testing in South Park
- Radon Testing in Ocean Beach
Not sure where to start?
Testing is the first step. Send a note describing your home, its foundation type, and any test results you already have.