Page | 006 2. Cooling. FM Global research has shown that cooling the surroundings is a critical factor to protecting the structure or surrounding occupancy because there is currently no way to extinguish an ESS fire with sprinklers. Gaseous protection systems do not provide cooling of the ESS or the surrounding occupancy.
3. Limited Discharge. FM Global research has shown that ESS fires can reignite hours after the initial event is believed to be extinguished. As gaseous protection systems can only be discharged once, the subsequent reignition would occur in an unprotected occupancy
The choice of a suppression system should be informed by liaison with a competent system designer who can relate the system choice to the risk identified and the duration of its required activation. Such a choice must be evidence based.5
Any calculations for sufficient water supply for an appropriate suppression system will need to be completed by a competent person considering the appropriate risk and duration of any fire.
Water run-off and potential impact on the environment, along with mitigation measures, should be considered and detailed in the Emergency Response Plan.
Lack of sufficient water supplies at a particular site location should not be considered as the basis for a suppression system choice. Such an approach could result in potentially ineffective and/or dangerous system designs.
Deflagration Prevention and Venting
BESS containers should be fitted with deflagration venting and explosion protection appropriate to the hazard. Designs should be developed by competent persons, with design suitability able to be evidenced.6 Exhaust systems designed to prevent deflagration should keep the environment below 25% of Lower Explosive Limit (LEL).
Flames and materials discharged as a result of any venting should be directed outside to a safe location and should not contribute to any further fire propagation beyond the unit involved or present further risk to persons. The likely path of any vented gasses or materials should be identified in Emergency Response Plans to reduce risk to responders.
Explosion/deflagration strategies should be built into the emergency plan such that responders are aware of their presence and the impact of their actions on these strategies.7
Where emergency ventilation is used to mitigate an explosion hazard, the disconnect for the ventilation system should be clearly marked to notify personnel or first responders to not disconnect the power supply to the ventilation system during an evolving incident.8
5 NFPA (2023) Standard for the Installation of Stationary Energy Storage Systems, para C.3
6 BS EN 16009:2011 Flameless Explosion Venting Devices; BS EN 14373:2021 Explosion Suppression Systems; BS EN 14797:2007 Explosion Venting Devices.
7 UL FRSI (2020) Four Firefighters Injured in Lithium-ion Battery Energy Storage System Explosion – Arizona, pp. 47-49
8 NFPA (2023) Standard for the Installation of Stationary Energy Storage Systems, para G.1.4.3.3
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