Final answer:
Radon measurement can be done with recirculating air-conditioning systems in use. Radon is a dangerous gas linked to lung cancer, and its levels inside homes can be measured for safety regulation compliance.
Step-by-step explanation:
When conducting a short-term radon measurement, using air-conditioning systems that recirculate interior air is permissible. Radon is a naturally occurring radioactive gas that can accumulate in homes, particularly in areas like basements. This colorless and odorless gas comes from the radioactive decay of uranium in soil and rocks, and its levels can vary significantly based on geographical location and the type of soil. Radon exposure has been linked to an increased risk of lung cancer, particularly among smokers. As such, many countries regulate radon levels and recommend measurement of indoor radon concentrations, especially before the sale of a house. To ensure safety, air-conditioning systems that recirculate air may be operated during short-term radon measurement procedures, as it does not significantly affect the results.