ABSTRACT
Designing a slotted hood can be envisioned as either a twoor three-step process, as outlined in the next three subsections. This chapter discusses design information for a canopy hood over an isothermal source from the Industrial Ventilation Manual's VS-99-03. In addition, a hot plume's buoyancy can cause it to rise into a canopy hood faster than it can exhaust that emission. It presents three design procedures for canopy hoods over a hot source: the first is for a canopy placed low over a hot source, and the second is for a canopy placed high over a hot source. The intent of the first three sections of the chapter was to provide readers with the basic principles of local exhaust hood selection and design including control velocities and the DallaValle equation. The resulting curtain of air draws off axis air away from the hood entrance while contaminants near axis of the hood are drawn into the exhaust portion of the hood.
