Which unit commonly expresses radon concentration in air?

Which unit commonly expresses radon concentration in air?

• A. Grays per liter
• B. Picocuries per liter
• C. Becquerels per liter
• D. Sieverts per hour

Answer: (B)

Radon concentration in air is about how much radioactive decay is happening per volume of air. The common way to express this is in picocuries per liter because it directly states the rate of decays per second in one liter of air, which is what affects exposure. A picocurie is 10^-12 curie, and since one curie equals 3.7×10^10 decays per second, 1 pCi/L is about 0.037 decays per second per liter, i.e., roughly 37 Bq/m^3. This unit is practical for public health guidance and for detectors that measure decay events in ambient air. Other units—like grays per liter or sieverts per hour—describe dose or dose rate, not concentration. Becquerels per liter would express the same idea in SI terms, but picocuries per liter is the conventional reporting unit in radon-in-air assessments.

Radon concentration in air is about how much radioactive decay is happening per volume of air. The common way to express this is in picocuries per liter because it directly states the rate of decays per second in one liter of air, which is what affects exposure. A picocurie is 10^-12 curie, and since one curie equals 3.7×10^10 decays per second, 1 pCi/L is about 0.037 decays per second per liter, i.e., roughly 37 Bq/m^3. This unit is practical for public health guidance and for detectors that measure decay events in ambient air. Other units—like grays per liter or sieverts per hour—describe dose or dose rate, not concentration. Becquerels per liter would express the same idea in SI terms, but picocuries per liter is the conventional reporting unit in radon-in-air assessments.