Which of the following components is essential in a radon control system?

Ventilation fans play a crucial role in a radon control system because they are responsible for actively reducing radon levels by creating air movement and facilitating the exchange of indoor air with outdoor air. This is particularly important in spaces like basements and crawl spaces where radon, a naturally occurring radioactive gas, tends to accumulate due to its origin in the soil. By pulling air from the ground and venting it to the exterior, ventilation fans help to lower the concentration of radon indoors, making them an essential component of an effective radon mitigation system.

While the other options might have some relevance to indoor air quality or general building safety, they do not serve the specific purpose of lowering radon levels. Air filtration units can improve air quality by filtering out particles and pollutants but are not specifically designed to target radon gas. Building insulation is important for energy efficiency and maintaining indoor temperatures but does not directly affect radon concentrations. Radon detectors are valuable for monitoring radon levels but do not contribute to mitigation efforts; instead, they help homeowners assess whether a radon control system is needed. The integration of ventilation fans in mitigation systems directly tackles the issue of radon, making them a key element in controlling radon exposure.