Figure 4-10. Coefficient of entry for a variety of hood and duct shapes.
4-11. AIR FLOW SYSTEM SURVEYS
a. System Start-Up vs System Design Basis. Any ventilation system, be it
local exhaust for contaminant control or general ventilation for comfort, is designed in
terms of removing or redistributing a specified quantity of air at a specific velocity at a
total system pressure. An initial survey is the only time a valid comparison can be made
between the design basis and the optimum system performance.
(1) Sketch of the system. A sketch not necessarily to scale but
representative of dimensions should be drawn noting such items as hoods, elbows,
branchings, air cleaner, fan, and stack. Supply ducts, plenums, and diffusers should be