It's probably your State's adopted Fire Code that indicates when blanketing is required and references NFPA 69 as the subcode to follow. For my State, there are situations for both indoor & outdoor storage when inerting is required. Per IFC-2000 911.1, indoor threshold volumes are quite low. If your code uses NFPA 30 Table 2-1 (e.g. IFC-2000 3404.2.9.5.1) for outdoor setback distances, some distances are only allowed with an approved inerting system. Not uncommon for a code official to demand an inerting system for a variance to a setback/separation distance.
From nashaat To dideyjohn
Refer to the recommendation of:
-NFPA 11 Foam Extinguishing system
Which include the Fixed Foam Extinguishing system for flammable storage tanks,system design & optimum foam application rates.
-NFPA 13 , 13A , 13D & 13E For the cooling systems.
The above two NFPA standards could be useful for your subject.
REGARDS.