In PCM counting, what is the minimum acceptable width-to-length ratio?

• A. 1:1
• B. 2:1
• C. 4:1
• D. 3:1 or greater

Answer: (D)

In PCM counting, you identify fibers by their elongated shape using an aspect ratio: the particle must be at least three times longer than it is wide to be counted as a fiber. That means the minimum length-to-width ratio is 3:1. Since the standard criterion is stated as length-to-width, “3:1 or greater” is the threshold that includes all fibers that meet the minimum requirement (anything with a longer length relative to width also qualifies). The other options don’t meet that minimum slenderness: a more square shape (1:1) or a width too large relative to length (2:1) wouldn’t be counted as a fiber, while a ratio of 4:1 would still count, but it’s not the minimum.