Dilution and Local Exhaust Ventilation - Coursework Example

Ventilation is a widely used method employed for controlling hazards that are airborne. It is the process of moving contaminated air from a given work area and substituting it with clean air. The hazards that are removed include flammable vapors, toxic chemicals, dust, metal fumes among others (Nims, 1999). This paper seeks to analyse the local exhaust ventilation and the dilution ventilation and elaborate differences in their working principles.Both of these systems work to remove contaminants from a working area.

The contaminants are directed into an exhaust system where there are discharged into the atmosphere. These contaminants may pass through an air cleaner before emission into the environment. Both of the systems require to make up the 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).

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 to 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 exhaust or exhaust stacks discharge the contaminated air into the outdoor environment. They should not be located near the fresh air intakes, and they must have adequate flow rates to prevent re-entry (Nims, 1999).The dilution ventilation employs large exhaust fans which on the roof of the building or walls. The fans create pressure differences for suctioning the contaminated air from the room. A fan may be required for enabling makeup air into the room to replace the exhausted air. The patterns of air movement and the placement of the inlet relative to worker location are critical in ensuring that the contaminated air is removed from the worker breathing zone.

A plenum may be encompassed in the clean air inlet area for the system to be more effective (Nims, 1999).In conclusion, ventilation is of paramount importance when it comes to the working area. The dilution ventilation system works on the principle of drawing contaminated air generally from the room. The local exhaust system removes contaminated air from a local source by utilizing a hood. It is more sophisticated and expensive to install but is best suited for toxic and highly flammable contaminants.

Fans are employed in both systems so as to create pressure differences and allow for the suction of contaminated air away from the working area. This contaminated air is then discharged through an exhaust system.