Compare and Contrast the Basic Principles of Dilution and Local Exhaust Ventilation

Ventilation is a mechanical system where fresh air is allowed to enter in a building whereas the contaminated air is removed indoor.There are two basic types of mechanical ventilation systems: the dilution ventilation system and local exhaust ventilation.This paper looks at ventilation as a practice that helps minimize the contamination from the airborne contaminants by removing vapor, dust and fumes (Canmet, 1992).

In industrial systems, ventilation is normally designed in sucha way that the velocity and amount of air being exhausted is controlled.Ventilation is important since it maintains temperature and humidity levels, continuously supplies fresh air from the outside, reduces the potentiality of hazards and dilutes contaminants (Canmet, 1992).In an industrial setting, ventilation system eliminates hazardous materials and alternates them with less lethal chemicals.The system has parts including air intake, ducts used to move air, devices that clean the air and fans that bring in air from the outside.Dilution ventilation minimizes contaminants concentration by both the air that is contaminated and the one that is not contaminated. On the other hand, local exhaust captures pollutes anddrains them outside (Canmet, 1992).

Dilution is also referred as general ventilation and uses large fans placed on roofs or walls to exhaust large volumes of air from a building.It ventilates the entire workplace as it distributes the pollutants. When controlling chemical pollutants through dilution, some factors need to be taken into consideration such as toxicity should be moderate andamounts of pollutants generated needs to be low. Dilution has some limitations since it does not remove all the contaminants and is not effective in the removal of metal and dust fumes (Canmet, 1992).

On the other hand, the local exhaust system is used in controlling air contaminants by trapping the contaminants near the source. It is effective as compared to the dilution ventilation since it can control deadly chemicals .In contrast, the dilution ventilation, allows contaminants to spread throughout the worksite. It is normally used where the amount of fumes being generated is high, there are serious health risks posed by the air contaminants andemission sources are few. Dilution ventilation is cheaper, requires less maintenance, effective when controlling low toxic and flammable chemicals as contrasted to local exhaust ventilation which requires high maintenance costfor installation, design and also the equipment.