How to Know if a Radon Mitigation System Is Working

Ensure that the radon mitigation system is set to its normal functioning state (that is, fans are turned on, the system is plugged in). Ascertain the manufacturer's or installer's performance specifications of your system, and note the expected or guaranteed performance numbers. (Radon gas concentrations are typically measured in picocuries per liter (pCi/L).)

Check the system's vacuum monitor. Some mitigation systems include a simple indicator device using columns of a colored liquid inside a curved tube. If the two columns in the tube are at or near the same height, there is a problem with system air pressure. If the two columns' heights are well-separated, the air intake fan is working properly.

Confirm intake airflow. Mitigation systems work by sucking radon-laden air out of the spaces underneath a building.

Some radon mitigation systems have check ports, or small holes in the basement floor that can be used to test airflow. Hold a smoke pencil or lit cigarette next to the port or hole, and closely watch the direction of the smoke. If the smoke is sucked into the hole, the system intake is working properly. If the flow is weak or absent, there's a problem affecting intake and sub-floor ventilation.

Check exhaust performance. Locate the exhaust vent or vents and determine whether air is in fact being blown out. A weak or absent airflow suggests problems in the motor, fan, piping or intake.

Take a direct radon measurement. This can be done by contacting a professional tester or by using an Environmental Protection Agency-certified home/premises test kit.

Start by using a short-term test kit. Follow the instructions on the kit package. These tests come in a small box, and usually need to be activated and left undisturbed in the lowest occupied floor of the home or building for two to three days. After this, the kit is returned to a testing laboratory, which then sends results back to the customer. The EPA has designated a radon concentration of 4 pCi/L (and above) as the "action level" at which mitigation is warranted to reduce airborne radon.

Contact the mitigation system installer or a radon professional. If your radon mitigation system seems to be performing below specifications, or is failing to sufficiently reduce radon concentrations, work with an expert to resolve the issue and establish a less hazardous indoor radon level.