Gen 4 Off-gas &
Thermal Runaway
Detection & Action for AI racks
and battery rooms

• Why the batteries are in the rack: they smooth the power feeding the rack and keep the liquid cooling running when the power bus to the rack is interrupted. A GPU rack that loses its cooling becomes a hazard in its own right.
• Room level detection does not hold: in a battery room, vented gas rises to a detector at the ceiling. In the white space the rack fans push the air out of the rack into an open, climate controlled hall with no containment. The gas does not reach a ceiling detector in time to tell you which rack is in trouble.
• Stage 2 or Stage 3: off-gas starts at venting and continues through thermal runaway. An off-gas only sensor cannot tell which stage the rack is in. The D-OFFGAS-RUNAWAY reports the thermal runaway signal separately.
• Action per rack: two relays in each sensor act on the rack that is in trouble, within seconds, without a round trip to a central controller.
• What is at stake: a single GPU rack represents millions of dollars of equipment. Knowing which rack, and which stage, decides the response.
• Not an LEL detector: the thermal runaway signal is a presence signal, not a concentration measurement. Where NFPA 855 and NFPA 69 call for LEL detection to drive ventilation, the R-GAS-FLAMMABLE does that at room level.

• Targeted chemistry: designed for the carbonate electrolyte vapors released during first venting: DMC, DEC and EMC.
• Two gas indices: the sensor reports a VOC index and a NOx index, each 0 to 500, so it reads more than one sign of a cell in distress.
• Rate of rise and absolute level: alarm on how fast the VOC index rises, on its absolute level, or both. Per rack placement keeps the trend meaningful and points to the rack that is venting.
• Self adapting baseline: the absolute level is measured against a baseline each sensor learns from its own rack, so a steady background in the hall reads as normal. Background compensation sits in every sensor, without separate reference sensors.
• Validated sensing technology: the off-gas sensing technology was validated in an independent test series run by Fire and Risk Alliance. In three releases of real LFP thermal runaway gas, it detected the gas in all three tests.
• Environment included: temperature and relative humidity are measured in the same sensor.
• Stage 2 is where Gen 4 starts: off-gas detection is the first warning. Thermal runaway detection, the second and distinct signal, is what sets the D-OFFGAS-RUNAWAY apart.

• Discrete signal: the sensor reports Thermal Runaway Detection as OK or Triggered, a separate output from the VOC and NOx indices, not a threshold on them.
• Dual confirmed: two independent sensing elements, from two different manufacturers, must both detect the thermal runaway gas before the state turns Triggered. A single element cannot raise it on its own.
• Validated sensing technology: the thermal runaway gas sensing technology was validated in the same Fire and Risk Alliance test series. In three releases of real LFP thermal runaway gas, it detected the runaway gas in all three tests.
• Speed: detection within seconds once thermal runaway starts, because the logic runs in the sensor and not in a remote controller.
• Stage 2 and Stage 3 in one sensor: one in rack sensor covers off-gas venting and thermal runaway. Off-gas only detection systems stop at Stage 2 and leave the runaway event to the smoke detector.
• Action follows detection: the Triggered state drives the embedded relays at the rack and is available through the P-BASE-8 over SNMP, Modbus TCP and BACnet IP.

• Two relays built into every sensor: each configurable normally open or normally closed, rated max. 30 VDC and max. 2 A. No add on, no external module.
• Assignable to any alarm: each relay is assigned to the alarm of your choice, off-gas, thermal runaway or any other condition, so the two stages can drive two different responses or the same one.
• In rack action: trip the rack contactor or battery breaker, signal the BMS, drive a local beacon or feed a monitored input on the fire alarm control panel, wired at the rack rather than run back to a central module.
• No central relay module: off-gas only systems place their relays in a separate module at the controller. Here the contacts are where the event is.
• Independent of the network: the relay decision is taken in the sensor, so the contact operates whether or not the base unit, the network or the BMS is reachable at that moment.
• Still reported centrally: the alarm and thermal runaway states remain available through the P-BASE-8 over SNMP, Modbus TCP and BACnet IP.

• Onboard detection logic: the off-gas indices and the thermal runaway signal are evaluated in the sensor, not after a round trip to a central controller.
• Onboard action: the relay decision is taken in the same device that detects, so detection and action follow each other within seconds.
• No single point of failure in the path to action: the contact operates whether or not the base unit, the network or the BMS is reachable at that moment.
• Reported centrally: the P-BASE-8 still collects readings, alarms and relay states from every sensor and exposes them over SNMP, Modbus TCP and BACnet IP.
• The alternative: off-gas only systems send raw sensor data over a hub and a network to a central controller that runs the algorithm and drives a separate relay module. Every hop adds latency and a point of failure between the rack and the action.

• P-BASE-8 only: the D-OFFGAS-RUNAWAY requires the P-BASE-8 base unit. It does not run on the BASE-PI-5-24V or BASE-PI-6. Existing installations on those base units add a P-BASE-8 for their Gen 4 sensors.
• One cable: a standard RJ45 CAT 6/7 cable carries both data and power from the base unit to the sensor, up to 100 m (330 ft) subject to cable quality and interference.
• Nothing in between: no hubs, no terminators, no dedicated power or network switches, no industrial PC as a controller and no separate relay module.
• Standard cabling: RJ45 CAT 6/7 is stocked everywhere and terminated by any installer. No proprietary cable or connector.
• Low power: 416.85 mW per sensor, drawn from the base unit.

Gen 4 against the legacy system

• Independent laboratory: the test series was run by Fire and Risk Alliance.
• Real thermal runaway gas: gas collected from an LFP cell driven into thermal runaway, released into a test enclosure three times. Not a bottled calibration gas.
• Both stages: the off-gas sensing technology and the thermal runaway gas sensing technology each detected the gas in all three tests.
• Report on request: the test report is available to directly concerned parties. Ask your question
• Patents pending. Certification to UL standard pending.
• All evidence on one page: listings, test results and patent status on the Evidence & Validation page.

• In the rack: D-OFFGAS-RUNAWAY, off-gas and thermal runaway detection, with two relays for local action.
• Row and room level: R-GAS-FLAMMABLE, off-gas and flammable gas detection, ETL Listed to UL 2075, as required by NFPA 855 and NFPA 69.
• One platform, one integration: both sensors report over the same open protocols, so the BMS, fire panel and DCIM see one system, not two.

• Proximity to the source: off-gas disperses and dilutes as it travels. On a fully populated rack, a single sensor can be several cells away from the one that vents. A second sensor keeps the detection point close to wherever the event starts, top or bottom of the rack.


• Rate of change over absolute level: a rising VOC or NOx index is far more informative than any single reading. Per rack placement is what makes that trend meaningful. A shared sensor covering several racks dilutes the signal and delays detection.


• Localisation and action: per rack sensors identify which rack is venting, not just that something in the room is, and the relays act on that rack.


• Cabling: the Class A loop is designed for exactly this density: a row of racks, two sensors each, on one loop back to the P-BASE-8, with no sensor lost to a single open.


• In an AI rack: mount at the battery shelf, typically towards the bottom of the rack, where the battery backup units sit.


• Placement: mount where vented gases will accumulate, following the airflow of the cabinet or enclosure.