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Thread: Air Intake Stack Height for Purged Buildings (NFPA 496)

  1. #1
    Join Date
    Aug 2007
    Houston, Texas

    Air Intake Stack Height for Purged Buildings (NFPA 496)

    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?
    Dan Marr

    "Real world Knowledge isn't dropped from a parachute in the sky but rather acquired in tiny increments from a variety of sources including panic and curiosity."

  2. #2
    Join Date
    Apr 2004
    Mission Viejo, CA
    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.
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

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