ABSTRACT
This chapter is only an introduction to local exhaust ventilation and all of the important topics herein will be repeated in more detailed and testable forms within a specific later chapter. The first definitions separate ventilation systems into two broad categories: general ventilation systems and local exhaust ventilation [LEV] systems. An LEV system may also contain an air cleaner and an exhaust stack. The necessity for air emission control is determined by the nature of the contaminant, the location of the exhaust stack, and air quality regulations. In almost all jobs, the industrial hygienist must be able to talk to the people responsible for the operation of the ventilation system in their language and to anticipate the effect on system performance of changes within a ventilation system. There are guidelines for design, but there are virtually no existing models that will predict exposures before a system is built.
