A Turning Point for Early Fire Detection: Why UL 2684 Listing Could Change Fire Protection
For decades, fire protection has largely been built around detecting the signs of a fire once an event has begun. Smoke, flame, and heat detection remain critical technologies, but they generally only address one question: How quickly can we recognize a fire?
Thermal imaging introduces a different possibility: How early can we recognize the conditions that could lead to one?
That is what makes the Teledyne FLIR A40 and A70 (Axx-Series) becoming the first thermal imaging cameras to achieve UL 2684 listing such a significant milestone. Thermal imaging now has a clear path from established industrial monitoring technology to a listed fire detection solution -- one that can be specified as part of fire alarm systems designed in accordance with NFPA® 72.
The implications could reshape how facilities think about early fire detection.
From Detecting Fire to Detecting Risk
Thermal imaging has been used for decades to identify abnormal temperatures in electrical systems, machinery, batteries, and industrial processes. Its advantage is straightforward: heat can provide an early indication that something is wrong.
Until now, however, there has been an important distinction between using a thermal camera to identify an overheating asset and using one as part of a code-compliant fire alarm system.
The standard provides a framework specifically for video and thermal image detectors used in fire alarm systems. With Axx-Series cameras achieving UL Listing, facilities can apply the early-warning capabilities of thermal imaging within a recognized fire detection framework.
That transforms thermal imaging from simply providing useful information about fire risk into technology that can play a direct role in the fire detection system itself. The camera can initiate a fire alarm through a compatible, listed fire alarm control unit. That is what UL 2684 covers: detectors that connect to a compatible power supply or control unit and operate as part of a fire alarm system.
The Warning Sign Is heat
—Thermal imaging spots abnormal heat before smoke or flame appears.
Conventional technology waits for a later signature: particles, visible smoke, flame, or heat at the ceiling. A thermal imaging fire detector measures the heat itself, before any of those exist.
Thermal imaging shows exactly where abnormal heat is developing, giving operators immediate location and context.
Why Earlier Detection Changes the Equation
Consider a battery cell module or server rack beginning to overheat, a failing electrical connection, or machinery generating excessive friction.
These conditions may produce a measurable temperature increase well before smoke or flame appears. A thermal imaging camera can continuously monitor for those changes and generate an alarm when predefined conditions are reached.
That additional warning time can fundamentally change the response.
Instead of reacting only after combustion begins, operators may have an opportunity to investigate the source, shut down equipment, isolate a battery, stop a process, or initiate an emergency response before the situation escalates.
In early fire detection, minutes matter. Sometimes seconds matter. The ability to recognize a developing thermal event sooner can create a larger window for intervention.
Seeing Precisely Where the Heat Is
A conventional detector reports that a device or zone is in alarm. A thermal image detector shows where: which asset, which part of it, and how hot it is. Whether it’s in a warehouse, a data hall, or on a production line, a UL-2684 Listed thermal camera turns an alarm into a location. Operators and response teams can go straight to the source instead of searching a large space for the cause. Because the same camera streams thermal and visible video, one device is both the detector and the verification feed. The people responding can know and see what they're dealing with before they arrive.
A New Tool for Complex Fire Risks
The milestone is particularly important as facilities become larger, more automated, and increasingly electrified.
Battery Energy Storage Systems, data centers, manufacturing plants, utilities, warehouses, rooftop solar installations, and recycling facilities can contain numerous potential heat sources spread across large or difficult-to-monitor areas.
Axx-Series cameras can continuously observe multiple assets and areas of interest within a single field of view, using configurable criteria such as temperature thresholds, rate-of-temperature-rise alarms, percentage-of-change notifications, and multiple monitoring zones.
Thermal imaging also provides something particularly valuable during an alarm: location and context. Operators can see where abnormal heat is developing rather than receiving only an indication that an alarm condition exists.
What Specifiers Need to Know
Thermal image fire detection has its own section in the 2025 edition of NFPA 72, Sec. 17.12. A few requirements shape every design.
Listing. The system and all of its components, hardware and software, must be listed for the purpose of fire detection (Sec. 17.12.1). The UL 2684 listing covers the camera as a detector connected to a compatible fire alarm control unit, so keep the fire detection path on listed equipment.
Design. Systems are designed to the performance-based requirements of Sec. 17.3 (Sec. 17.12.2.1), so a fire protection engineer designs the layout and the AHJ approves it. Location and spacing come from an engineering survey and the manufacturer's published instructions, and never exceed listed maximums (Sec. 17.12.2.2 and 17.13.5). Every detector needs a clear line of sight to the hazard it protects (Sec. 17.12.2.3).
Signals. The detector must be able to alarm on a temperature rate of rise (Sec. 17.12.7). It must send a supervisory signal if its lens is blocked or dirty enough to impair it (Sec. 17.12.6). Signals can go to other systems, such as a BMS or VMS, only through outputs the manufacturer provides for that purpose (Sec. 17.12.3).
Integrity. Settings and software must be protected from unauthorized changes (Sec. 17.12.4), and any change is tested under Chapter 14 (Sec. 17.12.5).
Where the 2025 edition is not yet adopted, in the US or abroad, the same listing supports a performance-based or equivalency submittal to the AHJ.
From Condition Monitoring to Fire Protection
For years, thermal cameras have helped maintenance teams find problems before they become equipment failures. UL 2684 listing brings that same early warning into the fire alarm system itself. The question is not only “How quickly a facility can detect a fire,” but “How early it can detect the conditions that lead to one?”
That shift—from reacting to fire to identifying risk earlier—is what makes this milestone potentially transformative for early fire detection.
The earlier you know, the more you protect.
Live thermal and visual views help operators configure and verify alarm conditions.
