In the fiber density calculation with isolated Microscope Constant, what is the denominator?

• A. Af
• B. Ac
• C. V x 1,000
• D. 1,000

Answer: (C)

Fiber density is expressed as fibers per unit volume, so you divide the counted fibers by the volume of air examined and convert to the standard units. In this method, the volume is often given in liters, and to report density in fibers per cubic centimeter you multiply that volume by 1,000 (since 1 liter equals 1,000 cubic centimeters). Thus the denominator is the sample volume in liters times 1,000, giving the volume in cubic centimeters. Af and Ac are related to areas and don’t belong in this denominator for this calculation. Using just the volume or a flat 1,000 would misstate the density because the actual volume must be converted to the correct unit.