What is the primary concern with a home's setup before conducting a radon test?

The primary concern with a home's setup before conducting a radon test is closing all windows and doors. This is crucial because radon measurement needs to reflect the natural radon levels within the home without interference from outside air. When windows and doors are open, fresh air can dilute the radon concentration, leading to inaccurate test results that may not truly represent the radon levels present in the home during a typical occupancy condition.

By sealing the home appropriately, you allow the radon gas, which originates from the soil and can enter the home through cracks and openings in the foundation, to accumulate and be measured more accurately. This provides a better assessment of the radon levels that occupants would actually experience.

The other options do not significantly impact the integrity of the radon test. For example, while ensuring light fixtures are off or removing furniture might improve conditions or aesthetics within the home, they do not directly affect the air quality or radon levels. Similarly, turning off the gas line does not have a significant connection to the measurement of radon, as radon emanates from geological sources rather than from household appliances or systems.