The limit of detection is given as a range in fibers per square millimeter. Which option expresses this range?

• A. 385 mm^2
• B. 100 f/mm^2 - 1300 f/mm^2
• C. 0.00785 mm^2
• D. 855 mm^2

Answer: (B)

The key idea is that the limit of detection is expressed as a density: how many fibers can be detected per unit area. That means the units should be fibers per square millimeter (f/mm^2), not a plain area.

A range written as 100 f/mm^2 – 1300 f/mm^2 shows the detectable fiber density from a lower to an upper bound per square millimeter, reflecting variability in detection capability. The other options give areas in square millimeters, which are not densities, so they don’t represent the limit of detection in fibers per unit area.