Compare and contrast the basic principles of dilution and local Essay

Compare and contrast the basic principles of dilution and local exhaust ventilation. Discuss at least five items for each and the elemtns for each system - Essay Example These contaminants may pass through an air cleaner before emission into the environment. Both of the systems require make up air so as to replace that which is exhausted, failure to which would lead to a decline in the room pressures. Both systems employ fans, which create a pressure difference allowing the flow of air along with its constituents, such as contaminants, into the exhaust system (Nims, 1999). Several differences exist between the two systems. To begin with, the local exhaust ventilation is characterized by the presence of a hood (inlet). The dilution ventilation lacks a hood. The hood is placed next to the source of emission; therefore, enabling the removal of virtually all sorts of contaminants by the local exhaust ventilation. In this respect, the local exhaust ventilation is best suited and perhaps the only choice for extremely flammable and highly toxic air borne contaminants. Only small amounts of air are exhausted by the local exhaust ventilation compared to the dilution ventilation. This means that dilution ventilation will require greater amounts of cooled or heated make up air than the local exhaust ventilation (Nims, 1999). The basic local exhaust of ventilation is comprised of the hood, ducts, cleaner, fan and exhaust stacks (Nims, 1999). The hood is placed near the source of emission of the contaminants. The ducts carry the contaminant in the local exhaust system. They should have minimal resistance for efficiency. Smooth and round ducts are ideal, and the flow rates in them should not be excessive as this will creates abrasion and noise. Air cleaners eliminate the contaminants before exhausting the air. State or federal regulations dictate the type of air cleaner to be employed. Fans are regarded to as the workhorses in the exhaust ventilation system. They provide pressure differences to suction the contaminants throughout the system and into the outdoor environment. The