RLAF velocity at working height

Is there any requirement for the velocity of air at working height. If yes then by which guideline/standard.
Any specific reason for keeing the velocity below 6" of HEPA filter only ?

in EU GMP Annex 1-MANUFACTURE OF STERILE MEDICINAL PRODUCTS: under point 3 for Grade A: … Laminar air flow systems should provide a homogeneous air
speed in a range of 0.36 – 0.54 m/s (guidance value) at the working position in open clean
room applications
. …