ISO14644-3 annex B: clarification on cleanroom supply airflow velocity

Hi everyone, thank you for providing such a useful platform !

I have a few questions regarding the section 4 of the annex B of the ISO 14644-3: I feel it’s quite unclear!

What’s said (in B.4.2.2) is this: “The number of measuring points […] should be the square root of 10 times of area in square meters but no less than 4. At least one point should be measured for each filter outlet or fan-filter unit”

1- “10 times of area in square meters” --> We felt the referred area is the total area of each ‘air-outlet’ in the room. We initially thought it was the area of the room itself but that didn’t make so much sense. Any idea?
2- What are “filter outlet” and “fan-filter unit” exactly? In some rooms, we measure the air velocity at each ‘air-outlet’ (sorry for my approximative english) but they don’t all have an individual filter.

Thanks in advance!