In this protocol, Volume is defined as which of the following?

• A. Flow rate x Time
• B. Sample Count x Time
• C. Number of fibers divided by number of fields
• D. Filter area divided by field area

Answer: (C)

Volume in this protocol is the density of fibers seen under the microscope, expressed as the average number of fibers per field of view. You tally fibers across a number of standard fields and then divide the total fiber count by how many fields were examined. This yields a normalized measure of fiber presence in the sampled area, which lets you compare samples even if different numbers of fields were looked at.

The other ideas don’t fit this specific usage: the actual air volume sampled would be flow rate times time, which is a different quantity used for concentration calculations in air sampling. A count times time or a ratio of areas doesn’t produce the fiber-density per field that this protocol defines as Volume.