Redding, California – A dangerous gas could already be building inside homes across Northern California as cool spring nights and shifting temperatures keep windows closed, allowing radon—known as the “invisible killer”—to accumulate indoors within hours. The risk can increase quickly when airflow is limited, especially in areas with larger day-to-night temperature swings.
According to the U.S. Environmental Protection Agency, radon is a radioactive gas that forms naturally in soil and can enter homes through foundation cracks, crawl spaces, and slab floors. While California is generally considered a lower to moderate radon-risk state, higher concentrations have been detected in parts of Northern California, including Shasta, Butte, and Tehama counties, where some homes exceed the EPA action level of 4 picocuries per liter.
In Redding and surrounding communities including Chico, Red Bluff, and Anderson, homes with crawl spaces and slab foundations are especially vulnerable during seasonal transitions. Residents often keep homes sealed overnight to maintain indoor temperatures, which can trap radon indoors. The California Department of Public Health warns that radon is the second leading cause of lung cancer in the United States, linked to about 21,000 deaths annually.
Radon exposure produces no immediate symptoms, making testing the only reliable way to detect it. Short-term test kits can return results within 48 to 96 hours, and mitigation systems can reduce indoor levels by up to 99 percent when properly installed.
Residents are urged to test homes now as conditions through April continue to support indoor buildup. Additional advisories may be issued as risks persist into early summer across Northern California.
