Fire and Rescue NSW Sets a 240-Minute Battery-Room Fire Rating and Questions Whether UL 9540A Tests Represent Enclosed Spaces

Fire and Rescue NSW now requires lithium-ion battery storage rooms in data centres to meet a fire resistance level of 240/240/240, meaning 240 minutes each for structural adequacy, integrity, and insulation of the bounding construction. The agency explicitly refused any reduction in those levels.

Four hours of rated containment is a demanding requirement. The more consequential element of the document is the reasoning the agency attached to it.

The testing claim. Fire and Rescue NSW stated that UL 9540A cell- and module-level tests do not adequately represent fire scenarios inside enclosed rooms. Most of that testing is conducted in open-air conditions. In an enclosed compartment, the agency argued, radiative heat feedback can accelerate fire growth beyond what open-air results predict.

That is a fire authority saying, in a published requirement, that the smaller-scale tests most often used for the technology do not capture how it behaves where it is installed.

The physical argument. UL 9540A is a test method for evaluating thermal runaway propagation. Its lower tiers characterise a single cell or module venting and burning. The results feed system design, separation distances, and the documentation that authorities having jurisdiction rely on to approve an installation.

A cell burning on an open test stand sheds heat into open air. The argument from Fire and Rescue NSW is that the same event inside a confined room produces radiative heat feedback that the open-air tests do not reproduce, and that the gap matters most precisely where batteries sit indoors in enclosed spaces. The objection is about the conditions the test runs under, not about the procedure itself.

What the agency required. Rather than rely on cell- and module-level data alone, Fire and Rescue NSW required that sprinkler design for systems above 50 kWh be validated either by large-scale fire-test data or by alignment with NFPA 855:2026. Those are two acceptable paths to the same evidentiary bar, and either one displaces the smaller-scale data as the sole basis for approval.

Australian jurisdiction. Fire and Rescue NSW has no authority over a building in Phoenix or the Bronx. No US code adopts its requirements by reference, and the rules are written for data centre uninterruptible power supply rooms, not for the broader population of indoor battery installations. As a matter of legal reach, it is one jurisdiction’s guidance for one building type.

The methodological objection does not depend on Australian law. Either open-air cell tests represent enclosed-room fire behaviour or they do not, and that is a question of physics rather than jurisdiction. The argument travels even where the regulation does not.

The standards trajectory. UL 9540A has reached Edition 6, and NFPA 855 in its 2026 edition tightened the regime for indoor systems. Both have shifted weight toward larger-scale validation and mandatory fire testing, and away from reliance on cell-level data alone.

Fire and Rescue NSW is not contradicting that direction. It is stating the rationale in blunt terms and applying it as a hard floor rather than a recommendation. The open question is whether US authorities having jurisdiction begin citing the same enclosed-compartment reasoning when they evaluate indoor installations, because the argument is now written down somewhere they can point to.

The competitive consequence for indoor systems. For any battery installed in a confined indoor space, the test tier behind the certification becomes a distinguishing fact rather than a footnote. A product whose safety case rests on cell- and module-level testing in open air carries a question that a product validated by large-scale, installation-representative fire testing does not. As the threshold for adequate evidence rises, that difference separates systems that clear it from systems that have to be re-evaluated.

The effect runs in two directions. A higher evidentiary bar rewards systems engineered and tested for enclosed operation from the outset. It also raises the cost and engineering burden for every indoor system, including purpose-built ones, because large-scale fire testing is expensive and the threshold keeps rising. The same trend that validates a product can later move past it.

The evidence standard. For most of the past decade, the industry treated a UL 9540A result as a finished credential. Fire and Rescue NSW is treating it as a starting point and asking what scale and setting produced the data. If that reframing spreads to US fire authorities and insurers, it changes what a battery installation has to prove before it is allowed indoors, and which suppliers can prove it.

The figure most likely to be quoted from the document is 240 minutes. The claim with the longer reach is the agency’s statement that the most commonly used tests do not represent the room the battery occupies.

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