Gas Detection for Battery Rooms & BESS | Indigi
Gas Detection for Battery Rooms, Data Centres and BESS: What You Need to Know
When people think about safety systems in battery rooms, data centres, and Battery Energy Storage Systems, fire detection and suppression are usually the first things that come to mind. But by the time a fire alarm triggers, the situation has often already moved past the point of early intervention.
Gas detection is the earlier warning system. It identifies hazardous gases at the point of release, before they reach concentrations that cause ignition, toxic exposure, or oxygen displacement. For battery-based environments specifically, gas release is the primary early indicator of a developing fault, and in many documented incidents it has been present for minutes or hours before any smoke or heat is visible.
This post covers the three main environments where gas detection is critical, the gases involved in each, and what an effective detection system looks like in practice.
The Core Hazard: Gas Release Before the Fire
The chemistry behind battery hazards is well understood. Lead-acid batteries produce hydrogen during the charging process. Lithium-ion batteries, under fault conditions including overcharging, physical damage, internal short circuits, or manufacturing defects, can enter a state called thermal runaway where internal temperature rises rapidly and releases a range of hazardous gases before any fire occurs.
Those gases include hydrogen (H2), carbon monoxide (CO), volatile organic compounds (VOCs) including electrolyte vapours such as diethyl carbonate (DEC) and dimethyl carbonate (DMC), methane (CH4), ethylene (C2H4), and in severe events, hydrogen fluoride (HF). Many of these are odourless and colourless. Some are heavier than air and accumulate in low areas near battery racks. Others rise to the ceiling. None of them trigger a standard smoke detector until it is too late.
A properly specified gas detection system identifies these gases at low concentrations, triggers ventilation and alarms before thresholds become dangerous, and integrates with existing fire panels and building management systems so that the response is automatic rather than dependent on someone noticing something is wrong.
Battery Rooms
What Happens in a Battery Room
Battery rooms are used to house the battery banks connected to UPS systems in data centres, hospitals, commercial buildings, industrial facilities, and telecommunications infrastructure. The most common battery type is still lead-acid, which produces hydrogen gas as a by-product of the electrochemical charging reaction.
Hydrogen is highly flammable and explosive at concentrations above 4% by volume in air. In a sealed or poorly ventilated room with multiple battery strings charging simultaneously, that threshold can be reached faster than most facility managers expect. The gas is lighter than air, so it accumulates near the ceiling and in any poorly ventilated pockets above the battery racks.
Australian Standards and the International Fire Code (IFC) require ventilation control and gas detection in battery rooms handling lead-acid batteries. The standard approach is a hydrogen sensor mounted high in the room, typically near the ceiling, with relay output connected to the ventilation system. When hydrogen reaches a preset threshold, usually around 1% by volume (25% of the lower explosive limit), the ventilation activates and an alarm is raised.
Lithium-Ion Battery Rooms
Facilities using lithium-ion UPS batteries face a more complex hazard profile. Under normal operating conditions, lithium-ion batteries are stable. Under fault conditions, the off-gassing profile is significantly more dangerous and varied than lead-acid.
VOCs are typically the earliest indicator of a developing thermal runaway event in lithium-ion cells, often appearing before any measurable temperature rise. CO follows as cell degradation progresses. HF appears in the later stages of a severe event and is acutely toxic even at low concentrations.
For lithium-ion battery rooms, a single hydrogen sensor is not sufficient. A combined approach covering VOCs, CO, and hydrogen provides the earliest possible warning across the full progression of a battery fault event.
Recommended Detection: Battery Rooms
The Evikon E2673 off-gassing detector simultaneously monitors hydrogen and VOCs on a single unit with maintenance-free sensors rated for approximately 15 years of service life. For larger rooms or facilities with both lead-acid and lithium-ion batteries, supplementary CO detection should also be considered.
Data Centres
UPS Battery Rooms in Data Centres
Every data centre operates a UPS system with a battery bank providing backup power during grid events. Those batteries sit in close proximity to IT equipment and, in many facilities, to personnel working in adjacent areas.
The hazard profile follows the same pattern as any battery room: hydrogen from lead-acid charging, and the full off-gassing sequence from lithium-ion faults. The difference in a data centre context is consequence. A gas event in a data centre battery room can force evacuation, trigger suppression system discharge, and cause downtime for the facility's entire IT load.
CRAC Refrigerant Leak Risk
Data centres also run CRAC (Computer Room Air Conditioning) precision cooling units that operate on HFC refrigerant-based circuits. A refrigerant leak in an enclosed server room or plant room can displace oxygen and create hypoxic conditions for personnel without any visible warning. Refrigerant gases are heavier than air and accumulate at floor level in server rooms and plant rooms where CRAC units are installed.
The Evikon E2638-HFC refrigerant detector covers a wide range of HFC and HFO compounds including R-32, R-410a, R-454b, R-134a, and others, with resolution down to 1 ppm and two user-settable alarm thresholds. It integrates with BMS and fire panels via 4-20 mA or RS485 Modbus RTU outputs.
CO2 Suppression System Monitoring
Many data centres use CO2 or inert gas suppression systems. After a suppression discharge, the CO2 concentration in the affected zone is hazardous to personnel re-entering the space. CO2 and oxygen monitoring provides a safe re-entry indication and ongoing post-discharge monitoring until the space is confirmed safe.
Recommended Detection: Data Centres
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Hydrogen and VOC monitoring in UPS battery rooms (E2673 or equivalent)
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HFC refrigerant leak detection in CRAC plant rooms (E2638-HFC)
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CO2 and oxygen monitoring in suppressed server rooms
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CO monitoring where lithium-ion batteries or backup generators are present
BESS Installations
The Most Complex Gas Detection Environment
Battery Energy Storage Systems present the most demanding gas detection challenge of the three environments covered in this post. BESS installations use lithium-ion batteries at scale, ranging from small behind-the-meter commercial systems through to multi-megawatt grid-scale containers. The gases released during BESS off-gassing and thermal runaway events cover a broader spectrum than either traditional battery rooms or data centres, and the consequences of a missed detection event are severe.
Thermal Runaway: Understanding the Sequence
Thermal runaway in a lithium-ion cell is a chain reaction. Internal damage, overcharging, physical impact, or a manufacturing defect can trigger a rapid temperature rise that produces gas, heat, and pressure. Once started, the reaction can propagate to adjacent cells and modules with very little warning.
The progression typically follows a sequence:
Stage 1 involves early off-gassing as VOCs and small quantities of CO begin to be released from a degrading cell. This stage can occur with no visible change in the battery system and is often detectable only by gas sensors.
Stage 2 sees CO and hydrogen concentrations increase as cell degradation accelerates. Temperature may begin to rise.
Stage 3 is full thermal runaway with active gas release, elevated temperature, and rapid progression toward ignition risk.
Gas detection is most valuable at Stage 1. By the time Stage 3 is reached, options for non-destructive intervention are limited.
Gases Released by BESS
The gas mix released during lithium-ion BESS faults depends on cell chemistry, state of charge, and failure mode, but commonly includes:
Hydrogen (H2), which is lighter than air and accumulates near ceiling level. Flammable above 4% by volume.
Carbon monoxide (CO), which is toxic at low concentrations, produced as cell degradation progresses.
VOCs including DEC, DMC, and ethylene carbonate, which are early-stage off-gassing markers and accumulate in low areas.
Methane (CH4) and ethylene (C2H4), flammable gases produced during active thermal runaway.
Hydrogen fluoride (HF) in severe events, which is acutely toxic and corrosive. In one full-scale fire test of a 1,000 kWh lithium-ion BESS, more than 200 kg of hydrogen fluoride was released.
Many of these gases are heavier than air and collect in low-lying areas near battery racks, cable trenches, and floor-level penetrations. Sensor placement must account for the density behaviour of each target gas to be effective.
Sensor Placement in BESS Environments
A common mistake in BESS gas detection design is treating all gases the same way. Hydrogen requires sensors positioned near the ceiling or at the top of enclosures. CO, VOCs, and HF require sensors positioned lower, near the battery modules and floor level. In containerised BESS installations, both high and low sensor positions should be included to cover the full gas profile.
Sensors should also be integrated with the site safety system so that a detection event triggers an automated response: ventilation activation, isolation of the affected battery string, alarm to the control room or fire panel, and if applicable, suppression system preparation.
Recommended Detection: BESS
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Combined hydrogen and VOC detection at each battery zone (E2673)
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CO monitoring throughout the installation
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Dual-gas transmitters where CO and combustible gas coverage is required in a single unit (Evikon E2660 series)
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ATEX-rated sensors where classified hazardous area requirements apply (Evikon E2670 series)
Designing an Effective Gas Detection System
Choosing the right sensor for each gas type is only the first step. Effective gas detection also depends on where sensors are placed, how they are integrated, and how the system responds when an alarm is triggered.
Sensor Placement
Gas placement must reflect the density of the target gas relative to air. Hydrogen is lighter than air and accumulates at ceiling level. CO, VOCs, HF, and CO2 are heavier and settle near floor level or at the height of battery modules. A sensor mounted in the wrong position for its target gas will miss the event it is designed to catch.
Integration
The most effective gas detection systems are hardwired into the facility's existing response infrastructure. Relay outputs connect directly to ventilation fans, audible and visual alarms, and fire panels. Analog 4-20 mA or 0-10 V outputs and RS485 Modbus RTU digital interfaces allow integration with BMS and SCADA platforms for remote monitoring, data logging, and alarm management.
Response
Detection is only effective if it triggers an appropriate response. At minimum, a gas alarm should activate ventilation to reduce concentration, raise an audible and visual alarm to alert personnel, and notify the control room or monitoring system. In high-criticality environments, the response should also include isolation of the fault source and preparation for emergency response.
Gas Detection as Part of a Broader Power and Cooling Safety Strategy
For data centres and critical infrastructure, gas detection does not sit in isolation. It is one layer in a safety system that also includes UPS power protection to maintain uptime during grid events, CRAC precision cooling to manage thermal load from IT equipment, and fire detection and suppression as the final layer of protection.
Indigi Power & Cooling delivers all three across the same project scope. Our gas detection service works alongside UPS installation and maintenance and CRAC unit servicing, meaning power, cooling, and gas safety can all be managed through a single contractor for critical infrastructure projects.
We supply the full Evikon MCI E2600 gas detector range including the E2673 off-gassing detector for battery and BESS applications, the E2638-HFC refrigerant detector for CRAC plant rooms, and fixed detectors covering more than 20 gas types for industrial and commercial environments across Queensland, New South Wales, Victoria, and Papua New Guinea.
Talk to Our Team
If you are specifying or retrofitting gas detection for a battery room, data centre, or BESS installation, contact Indigi Power & Cooling to discuss sensor selection, system design, and installation.
