Air Intake Stack Height for Purged Buildings (NFPA 496)

[DM2-Inc]

With respect to buildings located in Class I, Division 2 locations that use I'm trying to find out where, or if, there is a required height above grade that air used to pressurize a building must come from. Most of the buildings we see have a stack that take are into the pressurization system from about 25 feet above grade (or there about). I thought I'd see this in Chapter 7 or 8 of NFPA 496 but I don't see it there or in the Annex material.

If it's not specifically called out, how does one go about determining where to take the air from?

 

[rbalex]

You should be looking in Chapter 4; especially Parts 4.4 and 4.5. Basically, the requirement is the protective gas comes from an essentially clean source.