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Control Area - Design of Secondary Containment

Question asked by eric.snyder on Mar 29, 2018
Latest reply on Mar 29, 2018 by eric.snyder

For Reference - I'm working with NFPA1, 2009 and NFPA 13, 2013


NFPA1, calls for designing secondary containment for a Control Area to be sized to contain the largest vessel plus the design flow discharge of the fire extinguisher system over the minimum required system design area for a period of 20 minutes.  My question relates to what is considered the "design flow discharge".  Do I need to include the Hose Allowance Discharge when sizing the containment for a Control Area?  Doing so will require me to add 10,000 gallons of additional storage to the secondary containment (500 gpm x 20 min = 10,00 gallons ~ 1340 CF).


Per NFPA 13, Appendix A - Explanatory Material, A. the hose stream demand required by this standard is intended to provide the fire department with extra flow they need to conduct mop-up and final extinguishment of a fire at a sprinklered property.  This is not intended to be the fire department manual flow, which is determined by other codes/standards.  Also per NFPA 13, it is not the intent of this standard to require the sprinkler water demand to be added to the manual fire flow demand.  Per NFPA these are intended to be separate calculations.


Based on this, I would say I do not need to add the hose allowance flow to determine the size of the secondary containment for a Control Area.  Adding it would be rather punitive in my opinion.  In essence, the hose demand is used to ensure there is adequate water supply and pressure for the mop-up/extinguishment operations.  I seem to recall this is the case.  I have a consultant who believes otherwise. 


Your input is greatly appreciated.