What are the common types of hood?
The three common classes of hoods are: • enclosing, • receiving, and • capturing. Enclosing Hood Enclosing hoods, or “fume” hoods, are hoods surrounding the process or point where the contaminants are generated. Examples of completely enclosed hoods (all sides enclosed) are glove boxes and grinder hoods. Examples of partially enclosed (two or three sides enclosed) hoods are laboratory hoods or paint spray booths. The enclosing hood is preferred whenever possible. Figure 1 Partially Enclosed Hood Receiving Hood These hoods are designed to “receive” or catch the emissions from a source that has some initial velocity or movement. For example, a type of receiving hood called a canopy hood receives hot rising air and gases as shown in Figure 2. An example is a canopy hood located over a melting furnace. Figure 2 Receiving Hood Capturing Hood These hoods are located next to an emission source without surrounding (enclosing) it. Examples are a rectangular hood along the edge of a tank (as sho
