From NFPA 13 see below key being “shielding of combustibles is extensive”
These fires are very difficult to control and extinguish because the fire is deep seated. As a firefighter I hated these fires, a lot of work to pullout the burning garbage and separate it from the pile. Sprinklers are really just protecting the structure.
5.4.2* Extra Hazard (Group 2). Extra hazard (Group 2) occupancies shall be defined as occupancies or portions of other occupancies with moderate to substantial amounts of flammable or combustible liquids or occupancies where shielding of combustibles is extensive.
