I have a tough question. I'm trying to calculate the cfm over a surface in a room. assuming that the only airflow out of the room is an exhaust vent. I need to know how to calculate that CFM for the surface near the floor of the room, depending on its distance from the exhaust duct and the cfm inside the duct. I have one formula, but it seems incorrect to me: O = c (10*x^2 + A) Vx (where Vx is V sub x) O is the exhaust volume (at the surface in the room, I believe), cfm x is the distance from the center of the hood on the exhaust duct to the surface in question, ft A is the hood face area, not including the flange, sq ft Vx is the minimum capture velocity, fpm. c is a multiple for flanged or unflanged hood, .75 for flanged, 1 for unflanged. this formula produces results that are way too large. shouldn't the portion with the x be inversely effecting the results (divided) rather than directly effecting them (multiplied, whatever). Any input would be appreciated. thanks.