Under NIOSH-7400, what is the PCM flow rate range?

• A. 0.5-16 LPM
• B. Less than 10 LPM
• C. 0.5-2.5 LPM
• D. 1-20 LPM

Answer: (A)

Counting fibers with PCM means the amount of air drawn through the filter must be what yields a reliable, countable load on the filter without overloading it. The flow rate range is chosen to give that flexibility: it lets you sample longer at a low flow when concentrations are low, or sample for a shorter time at a higher flow when concentrations are higher, while staying within the method’s validated limits. This keeps the number of fibers on the filter within a practical, countable range and avoids issues like fiber overlap or under-sampling.

So the broad range of 0.5 to 16 LPM is the best fit because it covers the different workplace conditions you might encounter and supports obtaining valid, reproducible PCM counts. Narrower ranges would force you into suboptimal sampling times or flow rates, making counts less reliable.