Fire protection
A UPS and battery room holds the power that keeps everything else running, so its fire protection has two jobs: stop a fire without destroying the equipment, and get the critical load back safely afterwards. That depends on the battery chemistry, the gases the batteries can release, the way detection and suppression talk to the UPS, and what is done after a discharge.
The UPS cabinets, the switchgear, the battery cabinets and the cabling, from both the fire and the extinguishing. Honeywell's manuals list the properties that matter here: the agent is electrically non-conductive, leaves no post-fire residue and does no damage to protected equipment. Johnson Controls lists computer rooms and telecommunications and switchgear rooms among the hazards its inert gas protects.
What the agent cannot do is undo the fire. Smoke, soot and heat damage stay behind, and a discharge often comes with a planned power shutdown. Both are covered below.
Lead-acid batteries can, under the wrong conditions. C&D's manual for its VRLA batteries states that they emit no gas in normal operation but contain potentially explosive gases that may be released under abnormal conditions, such as a charger malfunction. It asks for enough ventilation that hydrogen in the battery area does not exceed two percent by volume, and notes that hydrogen above four percent by volume in air is explosive. EnerSys gives the same warning: under abnormal conditions, damage or misuse, hydrogen gassing, acid misting and leakage may occur.
The chemistry decides the room. ASHRAE's paper on power equipment explains that flooded (vented) batteries can evolve hydrogen in use, especially during recharge, and need a separate room with its own air supply, while VRLA batteries evolve very little hydrogen and can sit in IT spaces without special ventilation. Schneider Electric draws the practical conclusion for monitoring: VRLA batteries in the data centre do not need hydrogen sensors because they release none in normal operation, while wet-cell battery rooms are subject to their own code requirements.
Because overcharging is how a sealed battery turns into a gas source. The abnormal condition C&D names is a charger malfunction; a UPS rectifier that holds the wrong float voltage, or a hot battery cabinet, pushes the blocks toward gassing and heat. This is where battery service and fire protection meet. Float voltage, block temperature and resistance trends are exactly what a battery monitoring system watches, and a block that is drifting is replaced in a planned battery replacement long before it can vent.
For a fire in a battery room with lead-acid batteries, EnerSys's manual names carbon dioxide, foam or dry chemical as the extinguishing media to use; check the battery maker's own instructions for the batteries in your room.
The code requirements and the battery management. Vertiv's paper on lithium-ion battery safety explains that the 2018 edition of NFPA 1, the Fire Code, has a section (52.3) on deploying lithium-ion batteries in data centres. As Vertiv summarises it, fire suppression is mandated and rooms containing stationary storage batteries must be protected by an automatic sprinkler system; batteries need a UL 1973 listing, and an approved battery management system must monitor and balance cell voltages, currents, charge cycles and temperatures.
Lithium-ion batteries produce no gas in normal charging and discharging, Vertiv notes, though ventilation is still provided where the codes require it. Its paper also states that leading manufacturers build in quality and safety features aimed at minimising the chance of thermal runaway. Whether a clean agent is added alongside the sprinklers, and which one, is a design decision for the fire protection engineer and the authority having jurisdiction. The choice between the chemistries for a UPS is covered in lithium-ion vs VRLA.
In a planned order that everyone knows. Xtralis' aspirating detectors offer an Action level that can trip an equipment shutdown relay well before the Fire 2 level that releases the suppression system. Honeywell's commissioning test for its FK-5-1-12 systems includes verifying that dampers and doors close, the HVAC shuts down and power shuts down as intended, and its automatic systems release only when two or more sensors detect the fire, after a delay for people to leave.
Nothing should be restarted until the room is safe and the equipment has been checked. Honeywell's FK-5-1-12 manual says that after a deep-seated fire the space should stay tightly closed for at least 60 minutes, that the fire must be completely out before ventilating, and that nobody should enter without thorough ventilation or breathing apparatus. It also gives precautions for entering a space that contains the agent or its decomposition products. Inert gases, Honeywell notes, produce no decomposition products.
Once the room is safe, the UPS is inspected before it carries the critical load again: smoke and soot inside the cabinets, heat damage near the fire, the batteries, and the event log showing what the UPS saw. If the UPS was taken down by the fire system, it is restarted to the maker's procedure; if anything is in doubt, an emergency UPS repair visit checks it first. The fire system itself needs recharging before the room is protected again.
A fire protection engineer designs it, the authority having jurisdiction approves it, and the UPS and battery owner supplies what both need to know: the battery chemistry and layout, the heat load, which power feeds can safely be shut down and how the UPS restarts. Fire protection work is delivered through specialist fire protection subcontractors, and the interlock tests go best with people from both the fire and the UPS side present. Replacement batteries for data centre UPS are on the UPS battery page for data centres; UPS battery service covers testing and replacement.
Not in normal operation, according to Schneider Electric, because VRLA batteries release no hydrogen in normal use. Flooded batteries in a separate room are subject to their own code requirements, including ventilation.
C&D states that hydrogen above four percent by volume in air is explosive, and asks for ventilation that keeps the battery area under two percent.
Vertiv's summary of the 2018 edition of NFPA 1 says rooms with stationary storage batteries must be protected by an automatic sprinkler system. Your authority having jurisdiction sets what applies.
No. The room is kept closed, then ventilated, and the UPS and batteries are inspected before the UPS carries load again.
It can be designed to remove power. The design should state which feeds are shut down, and the test should prove it.
Sources, checked 2026-10-04:
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