I am writing you to request formal code interpretation on 2012 International Building Code (IBC) 412.4.5 regarding fire suppression for aircraft hangars.
“412.4.5 Fire Suppression. Aircraft hangars shall be provided with a fire suppression system designed in accordance with NFPA 409, based upon the classification for hangar given in Table 412.4.6”.
2012 International Building Code utilizing the 412.4.5 exemption 1 reads as follows:
“When a fixed based operator has separate repair facilities on site, Group II hangars operated by a fixed base operator used for storage of transient aircraft only shall have a fire suppression system, but the system is exempt from foam requirements.”
The way we interpret this section, the 2012 International Building Code (IBC) only provides relief from the foam requirement if a business meets the complete exemption criteria. In this case, exemption one. Upon further review, the fire sprinkler design standards referenced by the 2012 IBC are NFPA 13 (2010) and NFPA 409 (2011).
According to NFPA 13 (2010 edition) section 21.24.1 Design Requirements. Sprinkler systems installed in aircraft hangars shall comply with NFPA 409, Standard on Aircraft Hangars.
NFPA 409 (2011) does not provide any relief for storage of transient aircraft for its design criteria. It only calls out fueled and unfueled storage of aircraft within its design requirements.
NFPA 409 (2011) section 7.1.2 states “Group II aircraft hangar storage and service areas housing unfueled aircraft shall be provided with automatic sprinkler protection as specified in Chapter 12.’ Chapter 12 only applies to those hangars housing aircraft that have never been fueled or have had the fuel removed to comply with the definition for unfueled aircraft in Chapter 3.
In this Chapter, NFPA 409 (2011) 12.5.6 section calls out specific densities as follows: the design density of water from sprinkler systems shall be a minimum of 6.9 L/min/m2 (0.17 gpm/ft2) over any 464.5 m2 (5000 ft2) area, including the hydraulically most demanding area as defined in NFPA 13.
So if the structural code provides relief from the foam requirement in the fire sprinkler design, and if the hazard being protected is fueled transient aircraft. Am I correct in understanding that the only water based fire sprinkler design available to utilize for storage of fueled aircraft (transient or not) is the unfueled aircraft design assumption under NFPA 409?
Second question, is a water based fire sprinkler design adequate protection for fueled aircraft within an aircraft hangar regardless of its transient nature?