Radon concentration is typically reported in which unit?

• A. mrem/hr
• B. Bq/m3
• C. Sv/hr
• D. pCi/L

Answer: (D)

Radon concentration refers to the amount of radioactive radon in a given volume of air, so it is expressed as activity per volume. In residential testing, the common unit in the United States is picocuries per liter (pCi/L), which tells you how much radon activity is present in each liter of air. The SI equivalent is becquerels per cubic meter (Bq/m3); 1 pCi/L is about 37 Bq/m3, so levels can be converted if needed (for example, 4 pCi/L ≈ 148 Bq/m3). The other options are dose-rate units (mrem/hr, Sv/hr) that describe radiation dose rate, not concentration. Therefore, pCi/L is the typical unit used to report radon concentration.