What is the allowed quantity of lead in dry surface paint when testing with XRF?

What is the allowed quantity of lead in dry surface paint when testing with XRF?

• A. 0.1 mg/cm2
• B. 1.0 mg/cm2
• C. 10 mg/cm2
• D. 100 mg/cm2

Answer: (B)

XRF readings are most reliable when the paint layer isn’t heavily loaded with lead. The amount of lead per unit area, measured in milligrams of lead per square centimeter, needs to stay at a level where the X-rays can adequately penetrate the film and the detector can distinguish the signal from the surrounding material. For XRF screening, this practical limit is about 1.0 mg of lead per square centimeter of dry surface. If the dry film exceeds this loading, the reading can become inaccurate due to attenuation and matrix effects, and a destructive sampling approach may be needed to get a valid result. Thus 1.0 mg/cm2 is the appropriate threshold.

XRF readings are most reliable when the paint layer isn’t heavily loaded with lead. The amount of lead per unit area, measured in milligrams of lead per square centimeter, needs to stay at a level where the X-rays can adequately penetrate the film and the detector can distinguish the signal from the surrounding material. For XRF screening, this practical limit is about 1.0 mg of lead per square centimeter of dry surface. If the dry film exceeds this loading, the reading can become inaccurate due to attenuation and matrix effects, and a destructive sampling approach may be needed to get a valid result. Thus 1.0 mg/cm2 is the appropriate threshold.