What does an enclosing hood do in a local exhaust ventilation system?

What does an enclosing hood do in a local exhaust ventilation system?

• A. Exposes the source to the worker
• B. Completely or partially encloses the source and isolates the process
• C. Is the external duct to discharge outdoors
• D. Filters the air after it leaves the hood

Answer: (B)

An enclosing hood functions by surrounding the emission source to create a defined capture zone that isolates the process from the surrounding space. By completely or partially enclosing the source, it keeps contaminants near where they’re generated and channels them directly into the hood’s intake, pulling them away from the worker and the room. This at-source capture is the essence of local exhaust ventilation, improving capture efficiency and reducing exposure. The other ideas don’t describe the hood’s primary role: exposing the source to the worker would raise exposure, an external duct to discharge outdoors is about where the air goes after capture rather than how it’s captured, and filtering after it leaves the hood is an air-treatment step downstream rather than the hood’s function of containment and capture.

An enclosing hood functions by surrounding the emission source to create a defined capture zone that isolates the process from the surrounding space. By completely or partially enclosing the source, it keeps contaminants near where they’re generated and channels them directly into the hood’s intake, pulling them away from the worker and the room. This at-source capture is the essence of local exhaust ventilation, improving capture efficiency and reducing exposure.

The other ideas don’t describe the hood’s primary role: exposing the source to the worker would raise exposure, an external duct to discharge outdoors is about where the air goes after capture rather than how it’s captured, and filtering after it leaves the hood is an air-treatment step downstream rather than the hood’s function of containment and capture.