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Clarification required in water supply calculation in Aircraft hangar fire protection as per NFPA 409

Question asked by shivaji.santhanakrishnan on Jun 7, 2019
Latest reply on Nov 19, 2019 by shahadav

Details of the Aircraft Hangar:

We need to protect an Aircraft Hangar - Group 1 as per NFPA 409. Our protection scheme is Option 1. Foam water deluge system shall be installed under roof ceiling as primary protection & Low expansion foam monitors as secondary protection. 


Hangar Classification -       Group 1

Protection Scheme -          Option 1

Primary Protection -           Foam Water Deluge Systems

Secondary Protection -      Low expansion foam monitors


NFPA 409 - Question about fire water supply calculation:

Section -     the concentrate for the foam expansion deluge system shall be sufficient for 10 minutes                                foam discharge.

Section -   the total water supply duration shall be minimum for a duration of 45 minutes when supplementary                                systems are installed.

Please confirm, the water quantity for the protection is,

      a) design density in LPM x Operational Area x 45 Minutes (sufficient for compliance to and


      b) design density in LPM x Operational Area x 10 Minutes (sufficient only for compliance to


Thanks in advance,