ABSTRACT
The distance from the origin of pulvation to the null point can be thought of as the "maximum pulvation distance." For a lateral exhaust hood, the X-distance for calculation of contour area is often the distance from the face of the hood to the null point. Multidirectional, cold pulvation processes surrounded by booths may be analyzed by methods similar to those described for simple exterior hoods. If one could follow the action in slow motion, the initial outward pulsations would appear at first to indicate a loss of the dust to the hood influence, but this turns out to be temporary as it is recaptured, after spending itself, by the exhaust velocities that are still effective at the null point. This "capture" concept provides a useful and practicel basis for design in a wide variety of situations. It is noted that the X-distance from which the exhaust rate is calculated is the most remote from the source of suction.
