Local-exhaust ventilation at an ore transfer chute — Stokes settling vs. ACGIH capture velocity decide what escapes.
Every dust grain falls at its Stokes terminal velocity, vt = (ρp−ρair)·g·d²/(18μ) — fine (~5 µm) respirable dust settles at millimetres per second, coarse grit (~40 µm) settles orders of magnitude faster.
The hood's induced draw follows the classic ACGIH capture-velocity equation for a point source: vcapture(x) = Q/(10x²+A), where Q is the extraction flow and A the hood face area. A particle is captured only where this induced velocity beats its own settling + drift speed — which is why capture efficiency collapses fast with distance, and why the hood/skirt length (it shrinks the effective x) matters as much as raw fan power.
Water mist adds agglomeration: droplets stick to dry grains, inflating their effective diameter d — and since vt scales with d², even a modest mist setting makes dust drop out of the air and onto the belt almost immediately, at the cost of wetting the ore.
Motion is time-compressed ×6 for visibility; the ratios between settings stay physically faithful.