Columbia, South Carolina – A dangerous gas could already be building inside homes across the Midlands as spring temperature swings keep windows closed overnight, allowing radon—known as the “invisible killer”—to accumulate indoors within hours. The risk increases quickly when airflow is limited during cooler nights and early morning hours.
According to the U.S. Environmental Protection Agency, radon is a radioactive gas that forms naturally in soil and enters homes through foundation cracks, crawl spaces, and slab floors. South Carolina is considered a moderate radon-risk state, but elevated levels have been detected across Richland and Lexington counties, where some homes exceed the EPA action level of 4 picocuries per liter.
In Columbia and surrounding communities including Lexington, Irmo, and West Columbia, homes with crawl spaces and basements are especially vulnerable this time of year. Residents often keep homes sealed overnight to maintain indoor temperatures, which can trap radon inside. The South Carolina Department of Health and Environmental Control 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 critical. 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 the region.
