Which testing device provides a time-weighted average of exposure?

The testing device that provides a time-weighted average of exposure is a passive device. Passive devices, such as charcoal canisters or alpha track detectors, collect radon over a specified period, usually days or weeks, allowing them to develop a time-weighted average concentration. They do not require power to operate and rely on the natural diffusion of radon gas into the device, which makes them particularly useful for long-term monitoring.

In contrast, continuous radon monitors and electronic integrating devices typically provide real-time data and may average readings over shorter periods. Continuous radon monitors actively measure radon levels through ongoing sampling and analysis, providing immediate feedback on radon concentrations but not a time-weighted average over a long duration unless specifically programmed to calculate such. Similarly, electronic integrating devices can aggregate data over time but may not represent a true time-weighted average in the same way passive devices do.

Thus, the unique characteristic of passive devices to obtain a time-weighted average through unattended exposure makes them distinct and relevant in this context.