Gastight 2 : Describes a structure so constructed that gas or air cannot enter or leave the structure except through vents or piping provided for the purpose
NFPA 780 Standard for the Installation of Lightning Protection Systems, 2008 ed. http://www.uscg.mil/Petaluma/TPF/ET_SMS/Manuals/NF PA_780.pdf, (Std: Instll of Lightning Prot Sys - Amer) {347 NFC}