Local exhaust ventilation provides contaminant capture or dispersion at or near the source. This form of ventilation can range from the very simple, such as the use of fans, to the more complex, such as the use of an exhaust hood positioned at the source. In all instances, the goal is to blow or draw the contaminant away from the breathing zones of the workers. Examples of local exhaust ventilation include:
- exhaust fans positioned over furnaces,
- exhaust hoods for points of transfer on dusty operations,
- slot hoods for electroplating tanks,
- ventilated metal spraying booths,
- downdraft tables for finishing (grinding) of cast iron pieces, and
- portable exhaust hoods for welding operations.
Ventilation design is a complex and expensive process that needs to be undertaken by suitably trained engineers who are familiar not only with industrial ventilation design but also with methods used to control exposures and protect worker health. The designer should consider: (1) the regulations that govern the release of the workplace contaminant to the surrounding environment, and (2) the process operation, including any materials used and the frequency with which they are handled. Particular attention should be paid to packaging processes involving fine materials. With respect to process operations, it is less expensive and more effective to use specialized and dedicated equipment introduced at the design stage than to retro-fit such equipment to an existing facility.