Minimum angle for vent hood

[AlbertaMecchie]

I am designing a vent hood for an application about 3500 cfm. What is the minimum angle of the vent hood sides

 

[Compositepro]

There is none. Your hood has to capture whatever fumes you are dealing with, and that has nothing to do with sidewall angles. Often hoods are just cubic plenums.

 

[willard3]

There is no minimum angle, but any angle will have an associated pressure drop which you find in SMACNA manuals.