Local Exhaust Ventilation

Mechanism

Many industrial processes release airborne contaminants into the workplace. The inadequate control of these can allow them to enter the breathing zone of workers' resulting in inhalation exposure. One method of minimizing exposure is to apply extraction at the source of the contaminant generation, thereby removing the hazard before it enters the workplace air. This technique is usually referred to as local exhaust ventilation (LEV).

Local exhaust ventilation involves the capture of air contaminants at a source. A local exhaust ventilation system consists of a hood or enclosure to capture a contaminant, an air pollution control device to clean the air, and an air mover to provide air flow through the system. These systems range from small portable units, such as a high-efficiency particulate Air filter (HEPA)-vacuum system to extensive, permanent installations typical of large industrial facilities.

Highlights

This type of system is usually the preferred control method if:

Air contaminants pose serious health risk

Large amounts of dusts or fumes are generated

Increased heating costs from ventilation in cold weather are a concern

Emission sources are few in number

Emission sources are near the workers' breathing zones

In a general way, a local exhaust system operates similar to a household vacuum cleaner with the hose as close as possible to the place where dirt would be created.