B/nb stands for

• A. The number of fibers counted per number of fields in a blank
• B. The volume of blank samples
• C. The density of blanks per area
• D. The total fibers in a blank

Answer: (A)

In microscopic fiber counting, you compare observations by how many fibers show up in each view, so you get a consistent, comparable measure. B/nb means taking the total number of fibers you counted (B) and dividing it by the number of fields you counted in the blank (nb). The result is the average number of fibers per field in the blank sample. This per-field average standardizes the data because each field has the same approximate area, making it easier to compare across samples or runs and, when needed, convert to concentration using the known field area. It’s not about the volume of the blank, nor about density per area, nor the total fibers in the blank—the value is specifically the average fibers per field.