Which unit is used to express radiation exposure in the given guidelines?

• A. mR/hr
• B. mSv
• C. rem
• D. roentgen

Answer: (A)

Exposure rate is about how much ionizing radiation is present at a location per unit time. In field guidelines this is given as milliroentgens per hour because it directly shows how intense the radiation is at that moment. The roentgen is an older exposure unit and is not typically used as the instructional rate in modern guidelines. Dose-related units like millisieverts or rem measure biological effect or energy deposited in tissue, not the instantaneous exposure rate. So the unit used to express radiation exposure in the guidelines is milliroentgens per hour.