What is the primary purpose of using a charcoal canister in radon testing?

The primary purpose of using a charcoal canister in radon testing is to capture and absorb radon gas. Charcoal canisters are designed to adsorb radon, allowing for the measurement of its concentration over a specified period. When air containing radon passes through the charcoal, the gas adheres to the surface of the charcoal material. After the collection period, the canister is sent to a laboratory for analysis, where the amount of radon absorbed can be quantified. This process enables accurate measurement of indoor radon levels, which is crucial for assessing health risks associated with prolonged radon exposure.

The incorrect options focus on unrelated functions: measuring temperature does not pertain to radon collection, filtering out other gases is not the primary role of charcoal canisters, and providing a visual indication of radon levels does not occur with canisters, as they require lab analysis to determine radon concentration.