Radon is a silent intruder. You can’t see it. You can’t smell it. You can’t taste it. It is a colorless, odorless radioactive gas. It comes from the natural breakdown of uranium in the ground. Outdoors, it’s harmless. But indoors, it can be deadly.

Radon seeps through narrow spaces, including offices and schools, into homes. Such as:

• Cracks in concrete floors and walls
• Openings around pipes and wires
• Gaps in crawl spaces and sump pumps

Once inside, it can build up to dangerous levels. Radon is a dangerous gas according to the Environmental Protection Agency (EPA). Lung cancer is the second major killer in the U.S. due to exposure to it, following smoking. The scary part? You may live with high radon for years without knowing it, as it is colorless, and odorless. 

In this guide, we’ll explain why radon is dangerous. Where is it most commonly found? How does testing work for homes and commercial buildings? This guide will also cover the health risks of long-term exposure. Moreover, we will explore the Local California regulations that you should know.

Radon is the product of the natural radioactive decay of uranium. It is present in soil, rock, and water. Uranium is intrinsically decaying to radon gas. This gas moves through the ground and can enter buildings through the foundation.

Once indoors, radon doesn’t just vanish. It collects in the air you breathe. The threat of radon is that it has radioactive minute particles. If these particles are inhaled, they could damage lung tissue. Over time, that damage can turn into lung cancer.

Radon is of harm particularly harmful to children as their lungs are still in their developmental stage. It also poses a risk to the ageing population whose respiratory system is poor. However, Smokers are the most prone people whose lung tissue is already compromised. 

There are no early warning signs. No coughing. No headaches. Just invisible damage happening day by day.

Radon exists in all states, but there are radon-prone areas in the United States. Some of the areas to which Southern California can be subdivided are Pasadena, Santa Clarita and Palos Verdes. It happens that certain soils and rock formations emanate more radon. 

The EPA has developed developmental zones. These zones categorize areas to consider risk EPA Radon Zones Map. The zones are categorized into three areas: 

• Zone 1 (> 4.0 pCi/L): highest potential
• Zone 2: medium potential
• Zone 3: low potential

Natural higher radon levels exist in some areas in California that are mountainous and rocky. Common sources are granite-rich soils, such as those in some of the Sierra Nevada. This can even have problems on the beaches where the houses are constructed on old river banks or the fill dirt. The California Geological Survey offers radon data for different regions. You can check your area online. 

The right inspections prevent project delays and the risky projects or the budgets. Properly framed inspections safeguard schedules, jobs and project budgets. I

Testing is the only way to know if radon is a problem. You can’t rely on smell or sight. 

A. Residential Testing

• Short-term tests: 2–7 days. Uses charcoal canisters or digital devices. Good for quick checks.
• Long-term tests: 90 days or more. Gives a more accurate yearly average.
• DIY kits: Cheap and easy to buy at hardware stores. Take one step at a time up a ladder. 
• Professional testing: The testing exercises are performed by an accredited tester. They employ calibrated devices to get reliable outcomes.

B. Commercial Building Testing

Commercial spaces—like schools, hospitals, and office buildings—need bigger testing plans.

• At least 10% of ground-contact rooms are tested.
• Frequent use of continuous radon monitors (CRM) for ongoing Readings. 
• In some states, this testing is required in the day care facilities and in public schools.

C. Regulatory Guidelines

• The action level set by the EPA is 4.0 pCi/L. 
• Most professionals (and in California) advise that action should be taken at and above 2.0 pCi/L.

Radon is radioactive and emits radioactive particles. These particles adhere to dust and other airborne particles. They become lodged in your lungs when you breathe in. This, for years, exposure results in death. Especially if you’re a smoker living in a radon-rich home.

This radiation destroys lung tissue over the years. Such damage may lead to mutation of the cells, and this is how cancer begins.

Key facts:

• In the U.S., one can find that radon causes more than 21,000 deaths in the country each year due to lung cancer (EPA). 
• A person under exposure to radon, even when a smoker, is highly susceptible to cancer.
• There are no early symptoms. By the time cancer is diagnosed, it’s often advanced.

Construction methods which deter radon are often much cheaper and more effective. than remediation for an existing building. Therefore, it is a better business decision for developers and property owners. 

Constructors can easily install different systems for radon prevention. Such systems are passive venting, sub-slab depressurization, and vapor barriers under the slab. These systems keep radon from entering the indoor space during the construction phase of the project. 

These options help to decrease future maintenance costs. It is also better for the indoor air quality of the building’s occupants from the start.

The Los Angeles Department of Building and Safety (LADBS)and San Bernardino County Building and Safety require similar systems to be addressed on all public projects. It makes the system work safely and lawfully so as to guarantee the safety of the population’s health. Such upgradings would ensure that the project achieves WELL and Fitwel ratings.

These benefits indicate that the building provides a radon-safe environment. It also qualifies to achieve many other sustainability benchmarks. Each of these certificates will increase marketability. It also increases the long-term valuable conditions for the building.

If testing shows high radon levels, don’t panic. Fixes are available. Here are some common methods which can be used.

Most common method:

• Sub-slab pressure depressurization: New radon goes through a pipe and a fan system. This system leverages radon from underneath the building. It works its venting so outdoors.

Other methods:

• Crack seal floors and walls. 
• Better ventilation of crawl spaces.
• Install soil suction systems.
• Retest after fixes to confirm results.
• Maintain systems regularly. Fans can wear out over time.

If we talk about the cost of Radon testing, it doesn’t cost much as compared to the hazards it causes. So, here is a brief cost estimate for different types of projects. 

• DIY test kits: $15–$150.
• Professional home testing: $200–$600.
• Commercial testing: $1,000–$10,000+, depending on building size.
• Mitigation systems: $800–$2,500 for homes; higher for large buildings.

Compared to medical costs for lung cancer or potential lawsuits, testing is a low-cost investment. Also, homes with proof of safe radon levels can sell faster and for more money. Buyers appreciate the extra peace of mind. 

Testing not only adds to property value, but it also assists in real estate transactions. It helps to comply with HUD and CEQA regulations. In the long run, the ROI comes in the form of occupant safety, fewer liability risks, and easier permitting.

California counties and cities are enforcing more stringent regulations. However, the EPA’s guidelines are not federal laws. Radon review is part of LA County’s Onsite Wastewater Treatment Systems (OWTS) procedure. 

HUD requires federally funded housing to undergo testing. For indoor air quality evaluation of transportation infrastructure, Caltrans takes radon into account. States are urged by groups like AASHTO and FHWA to implement radon-safe design guidelines. It is particularly strict criteria for hospitals and schools.

In California:

• California Geological Survey maps radon-prone areas.
• California Department of Public Health runs a statewide radon program.
• HUD requires radon testing for federally financed multifamily housing.
• LEED, WELL, and Fitwel building certifications require radon testing as part of indoor air quality checks.

In Los Angeles County, local agencies like LADBS can require radon mitigation. Not following radon regulations could mean:

• Failed inspections
• Health violations
• Tenant lawsuits

Radon is an invisible killer. But it’s 100% preventable. Testing is simple, cheap and life-saving. As a homeowner, landlord or commercial developer, radon testing should be a routine safety measure.

Residents or employees of Southern California should determine in which radon zone they are located. Use a qualified radon professional. Rebuild every couple of years or following re-modelling. Timely action on your part will keep human lives safe, property value intact and safe legally. That is a worthy investment.

What is the safe level of radon in a building? 

Anything less than 2.0 pCi/L is safe. There is a need to mitigate levels that are above 4.0 pCi/L.

Do Southern California homes have radon problems? 

Yes. High levels can be found in areas with rocky ground or granitic ground, e.g. Pasadena, Malibu.

Is radon testing required in schools and offices? 

Yes. There are even counties in California that require radon testing for schools, hospitals etc. 

Who is qualified to conduct a radon test in California? 

Only licensed professionals certified by NRPP, NRSB, or a California-licensed geologist or engineer.

How often to test? 

Every 2–5 years, or after significant structural changes or mitigation.

Is radon disclosure mandatory in real estate transactions? 

Not legally required in California, but strongly recommended during escrow.