In order to reduce or eliminate any hazard from the work area, there are three methods that the safety professional must adhere to. These methods include Engineering Control, Administrative Control, and Personal Protective Equipment. One way to reduce or eliminate the concentration of hazardous materials from the workplace is through ventilation. Ventilation is basically divided into three categories, general, dilution, and local ventilation. In order to begin to understand ventilation, it is necessary to understand the principles of air movement. Air flow rates are calculated by multiplying the velocity by the cross-sectional area of the hood or duct in which the air flows. When using dilution ventilation, it is important to understand that the flow rate of fresh air is determined by contaminant generation, proper mixing, and target final concentration. The objective of dilution ventilation is to maintain a steady-state concentration, which is less than the threshold limit value (TLV) or permissible exposure limit (PEL) for the contaminant of concern.