What is a smear?

• A. A device used to measure contamination
• B. A type of contamination
• C. A method of measuring radiation from wiping cloth or paper over a surface
• D. A fixed contamination description

Answer: (C)

Smear refers to a wipe test used to measure removable surface contamination. In this method, a defined area is wiped with a clean cloth, gauze, or filter paper to collect any radioactive material that can be wiped off the surface. The collected material is then counted with a radiation detector to determine how much activity was removable from that surface. This distinguishes removable (smearable) contamination from fixed contamination, which remains on the surface after wiping. It’s not a device, not a type of contamination, and not a description of fixed contamination. The result is used to assess cleanliness and decontamination effectiveness, typically reported as activity per area (for example, dpm/100 cm2 or Bq/100 cm2).