BESS Thermal Runaway Emergency Response SWMS

BESS thermal runaway emergency response covers the pre-incident planning and the on-site response to a lithium-ion battery thermal event at a commercial or grid-scale storage facility. Thermal runaway is the self-sustaining exothermic failure of a lithium-ion cell, in which internal temperature rises uncontrollably, the cell vents flammable and toxic gas, and the event can cascade cell-to-cell and module-to-module. The response work covers establishing a vent-gas exclusion zone, de-energising and isolating the affected array, identifying hot cells with thermal imaging, applying cooling and maintaining a re-ignition watch (which can extend for many hours or days), ventilating and overhauling the container, handing off to Fire and Rescue, and the post-incident make-safe. This is hazardous, high-consequence work performed in a degraded environment, and it is treated as High-Risk Construction Work.

The vent gas from a lithium-ion event contains hydrogen, carbon monoxide, and hydrogen fluoride among other constituents — a mixture that is both flammable (with explosion risk in an enclosed space) and acutely toxic. Responders cannot rely on extinguishing a battery fire in the conventional sense; lithium-ion cells carry their own oxidiser and a runaway must be cooled and allowed to burn out under control while re-ignition is monitored. The work is governed by the safe-system-of-work principles in Managing Electrical Risks in the Workplace, the battery-system framework of AS/NZS 5139:2019, and confined-space entry to AS 2865 where a responder must enter a container-class enclosure.

This SWMS is jurisdiction-neutral within Australia and written to the model WHS framework. Victoria operates under the Occupational Health and Safety Act 2004 and OHS Regulations 2017 — check the VIC-specific variant for the local equivalents of the duties and codes cited here.

Hazards identified

13 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Eliminate close-approach risk by managing the event remotely wherever possible — establish a vent-gas exclusion zone on the windward side, control entry to it, and do not approach or enter the affected enclosure during active gassing or flaming if the situation can be stabilised from outside.
2. 2Pre-plan the response in cooperation with Fire and Rescue before any incident, with a documented site-specific emergency plan covering isolation points, access, water supply, exclusion-zone geometry, and a defined command hand-off to the fire service.
3. 3Isolate and de-energise the affected array at the array and DC level using the documented procedure to AS/NZS 4836, treating a thermally damaged array as live and unpredictable until proven otherwise, and never assume the inverter being open has de-energised the battery.
4. 4Continuously monitor the atmosphere for flammable gas, oxygen, carbon monoxide, and hydrogen fluoride from the exclusion-zone boundary, and prohibit any approach that would bring a responder into a flammable or oxygen-deficient atmosphere without engineered ventilation.
5. 5Apply cooling water to the enclosure exterior or affected module from a protected position to arrest propagation, and maintain a re-ignition watch with thermal imaging for the full period advised by the cell chemistry — potentially many hours or days — before stand-down.
6. 6Treat any entry into a damaged container-class enclosure as a confined-space entry to AS 2865 — entry permit, atmospheric clearance, continuous monitoring, a stand-by attendant, and a rescue plan — and only after the array is isolated and the atmosphere is proven safe.
7. 7Manage HF-contaminated firewater and surface residue as a hazardous substance — bund and contain run-off, prohibit skin contact, and decontaminate equipment and responders before they leave the hot zone.
8. 8Rotate responders and enforce work-rest cycles with active cooling and hydration to control heat stress during prolonged cooling and watch operations in encapsulating PPE.
9. 9Maintain housekeeping and hose management to control slips, trips, and falls across the incident scene, and light the area for the watch phase to control disorientation in residual smoke.
10. 10Use mechanical aids and team lifting for hoses, barriers, and cooling apparatus to control musculoskeletal injury during exclusion-zone set-up under time pressure.
11. 11Provide a documented post-incident psychological support pathway for responders and brief crews on the emotional load of high-consequence response before the event.
12. 12Provide PPE as the final layer — self-contained breathing apparatus or supplied-air for any approach to a gassing enclosure, HF-resistant chemical protection, arc-rated clothing where live DC is credible, and full structural fire kit during active fire — selected and fit-tested for each responder.
13. 13Verify responder competency and accreditation (electrical isolation competency, confined-space entry, BA/SCBA, and incident command) and conduct regular drills so the documented plan is rehearsed before it is needed in earnest.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

A commercial property in Western Sydney hosts a 2 MWh BESS in two outdoor container-class enclosures supporting a logistics warehouse. The asset operator must have an emergency-response plan in place before the network operator will sign off the connection. The operator takes this product, selects the NSW variant, and works with the local Fire and Rescue station to pre-plan the response. The plan fixes the isolation points, the windward exclusion-zone geometry, the water supply, and the command hand-off to the fire service. Some months later, a battery management system alarm and a smoke detection signal indicate a cell event in one enclosure. The site response team executes the SWMS: they establish the exclusion zone on the windward side, isolate the array at the DC level using the documented AS/NZS 4836 procedure, and begin continuous atmospheric monitoring from the boundary for hydrogen, carbon monoxide, and hydrogen fluoride. No one approaches the enclosure during active gassing. Fire and Rescue arrive and assume command per the pre-planned hand-off, applying cooling water to the exterior from a protected position. The team maintains a thermal-imaging re-ignition watch for the full period advised for the cell chemistry before stand-down. When the enclosure is later entered for hot-cell identification and overhaul, it is treated as a confined-space entry to AS 2865 — permit, atmospheric clearance, stand-by attendant, and rescue plan — only after the array is proven isolated. HF-contaminated firewater is bunded and managed as a hazardous substance. No responder is injured, and the documented response and the SWMS form the basis of the post-incident review submitted to the insurer and the regulator.

Related legislation

• Work Health and Safety Act 2011 (NSW) — Sections 19 (primary duty of care), 31 (Category 1 offence), 32 (Category 2 offence), 43-45 (duties relating to emergency plans)
• Work Health and Safety Regulation 2017 (NSW) — Sections 291 (HRCW definition), 299 (SWMS), 43 (emergency plans), 66-77 (confined spaces)
• AS/NZS 5139:2019 — Electrical installations — Safety of battery systems for use with power conversion equipment
• AS 2865-2009 — Confined spaces (atmospheric testing, entry permits, rescue arrangements)
• AS/NZS 1715:2009 — Selection, use and maintenance of respiratory protective equipment

Frequently asked questions