Local Exhaust Ventilation

Topic: What is Local Exhaust Ventilation?

 

Local Exhaust Ventilation also known as LEV is a type of ventilation system designed to capture contaminants at the point of generation. The primary advantage of using a local exhaust ventilation system is the ability it has to effectively remove the contaminant from the work area. Local exhaust ventilation systems are designed for specific application and tend to be more efficient in terms of energy consumption. A local exhaust ventilation system is made up of five components: a hood, ducts, an air cleaner, a fan and the exhaust.  

The first component of the LEV system is the hood, the hood captures the contaminants. There are three basic types of hood designs that can be used in the LEV system, one being the capture hood, the enclosing hood and the receiving hood. According to Basics of Industrial Hygiene the design and placement of the hood are crucial to the effectiveness of the LEV system; if the hood does not capture the contaminant, the entire system is not able to perform its intended function. The second component of the LEV system is the ducts. The purposes of the ducts are to carry the air and contaminants toward the outlet at the end of the LEV system. There are multiple different sizes of ducts; the size is related to energy loss. The third component of the LEV system is an air cleaner. “An air cleaning device is recommended and in some cases detected by regulations, for all air contaminants that pose a human or environmental hazard.”  Air cleaning devices can move many particles from the air including dust, and fumes. The fourth component in the LEV system is the fans. They are placed toward the end of the system, and are a crucial element in the system because they create the pressure difference that ultimately makes the entire system work. Lastly is the exhaust piece of the system. “The best design will allow release of air with minimal added pressure.” 

Basics of Industrial Hygiene by Debra Nims