What are the three things for protection against radiation?

• A. distance, humidity, shielding
• B. time, shielding, PPE
• C. distance, time, ventilation
• D. distance, time, shielding

Answer: (D)

Radiation protection hinges on three controls: distance, time, and shielding. These work together to keep your dose as low as possible.

Distance matters because radiation intensity falls off with distance. The farther you are from the source, the smaller your exposure becomes—often dramatically so. This is the inverse-square principle in action: a modest increase in distance can substantially reduce dose.

Time matters because the total dose is proportional to how long you’re near or exposed to the source. Shortening the time of exposure directly lowers the accumulated dose you receive.

Shielding matters because barriers absorb or attenuate radiation before it reaches you. The right shielding material and thickness depend on the type of radiation (for example, gamma rays require dense material like lead or concrete; beta radiation needs something to stop it but not necessarily as heavy; alpha radiation is easily stopped by a sheet of paper or skin).

PPE and ventilation can be part of a safety plan in specific scenarios, such as reducing inhalation of contaminated air or protecting against contact with contaminated surfaces, but they do not replace the fundamental dose-reduction strategies of distance, time, and shielding.