Scope NFPA 855 regulations apply differently, depending on ESS sizes, technologies and capacities. According to NFPA.org, the standard applies to lead acid battery ESS with a combined capacity of 70 KWh (kilowatt-hour) or more, while ESS using lithium-ion batteries requires a threshold of 20 KWh for NFPA 855 to apply.
Location There are greater risks for indoor ESS locations than outdoor ESS locations. Indoor, non-dedicated use buildings require fire-rate separation from nearby occupancies in the form of a 1–2-hour fire-rated wall. If the ESS is outdoors, it must be at least 100 feet away from other buildings and walkways.
Size and separation To prevent fires in ESS, NFPA 855 requires three feet of separation between every 50 KWh grouping of batteries. This rule also applies to the walls in the room.
Fire suppression and control Water is an effective extinguishing agent for most ESS fires, including lithium-ion battery ESS. To assist in fire suppression and control, NFPA 855 recommends installation of a sprinkler system in an energy storage system utilizing Li-ion batteries.
Utility and telecom applications Statements through NFPA 855 permit utility or telecommunications facilities to not comply with certain ESS and battery storage requirements because they serve as critical infrastructure and are already regulated by several bodies.