{
  "node": {
    "id": "term:gas-detection",
    "type": "Term",
    "label": "Gas detection",
    "properties": {
      "id": "gas-detection",
      "name": "Gas detection",
      "aka": [
        "off-gas detection"
      ],
      "section": "topic-safety",
      "definition": "Sensors in a pack or storage container that detect electrolyte vapour or hydrogen released before thermal runaway. Off-gas appears minutes before heat and smoke, which makes it the earliest practical warning.",
      "related": [
        "off-gas",
        "venting",
        "fire-suppression",
        "bms",
        "early-thermal-runaway-detection"
      ],
      "url": "https://lemonergy.com/learn/glossary/gas-detection/",
      "mentions": [
        "electrolyte",
        "thermal-runaway"
      ]
    }
  },
  "edges": [
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      "id": "edge:1774",
      "source": "term:gas-detection",
      "target": "topic:topic-safety",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
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    {
      "id": "edge:1775",
      "source": "term:gas-detection",
      "target": "term:off-gas",
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    {
      "id": "edge:1776",
      "source": "term:gas-detection",
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      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:1777",
      "source": "term:gas-detection",
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        "meaning": "Related context; not a causal claim"
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      "id": "edge:1778",
      "source": "term:gas-detection",
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      "type": "relatedTo",
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        "meaning": "Related context; not a causal claim"
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    {
      "id": "edge:1779",
      "source": "term:gas-detection",
      "target": "term:early-thermal-runaway-detection",
      "type": "relatedTo",
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        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:mentions/gas-detection/electrolyte",
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      "id": "edge:mentions/gas-detection/thermal-runaway",
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      "id": "topic:topic-safety",
      "type": "Topic",
      "label": "Safety and abuse",
      "properties": {
        "id": "topic-safety",
        "name": "Safety and abuse",
        "lede": "How cells fail dangerously, how that is tested, and what is built in to stop it.",
        "context": "Connect mechanisms with appropriate test evidence.",
        "example": "A low normal-load temperature does not demonstrate thermal-runaway containment.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/",
        "lesson_label": "Open degradation mechanisms"
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      "id": "term:off-gas",
      "type": "Term",
      "label": "Off-gas",
      "properties": {
        "id": "off-gas",
        "name": "Off-gas",
        "aka": [
          "vent gas"
        ],
        "section": "topic-safety",
        "definition": "The mixture released when a cell vents: electrolyte vapour, hydrogen, carbon monoxide, carbon dioxide and hydrocarbons, with hydrogen fluoride. It is flammable and toxic, and gas sensors detect it before smoke or heat in a storage container.",
        "related": [
          "venting",
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      "label": "Venting",
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        "id": "venting",
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        "section": "topic-safety",
        "definition": "The controlled release of gas and vapour from a cell whose internal pressure has risen too far, through a vent designed to open before the case bursts. The vented gas is flammable and toxic, so packs route it away from occupants.",
        "related": [
          "vent",
          "gas-generation",
          "thermal-runaway",
          "off-gas"
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        "mentions": []
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      "id": "term:fire-suppression",
      "type": "Term",
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        "id": "fire-suppression",
        "name": "Fire suppression",
        "section": "topic-safety",
        "definition": "Systems that cool or smother a battery fire: water mist and flooding for cooling, inert gas or aerosol for enclosed storage containers. Because the cell makes its own oxygen, suppression mainly limits spread and cools neighbours rather than extinguishing the failing cell.",
        "related": [
          "flammability",
          "thermal-propagation",
          "gas-detection",
          "stationary-storage",
          "firefighter-access"
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        "mentions": []
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      "id": "term:bms",
      "type": "Term",
      "label": "Battery management system",
      "properties": {
        "id": "bms",
        "name": "Battery management system",
        "abbr": "BMS",
        "section": "topic-pack",
        "definition": "The electronics and software that keep a battery inside its safe window: measuring every cell voltage and many temperatures, estimating SOC and SOH, balancing cells, computing current limits, controlling the contactors and reporting over the vehicle network.",
        "related": [
          "state-of-charge",
          "cell-balancing",
          "state-of-power",
          "cell-supervision-circuit",
          "contactor",
          "can-bus"
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        "url": "https://lemonergy.com/learn/glossary/bms/",
        "mentions": [
          "state-of-health",
          "cell-voltage"
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      "id": "term:early-thermal-runaway-detection",
      "type": "Term",
      "label": "Early thermal-runaway detection",
      "properties": {
        "id": "early-thermal-runaway-detection",
        "name": "Early thermal-runaway detection",
        "aka": [
          "thermal runaway warning",
          "thermal event detection"
        ],
        "section": "topic-safety",
        "definition": "Spotting a failing cell before it runs away, from the signals that precede heat: a voltage drop or abnormal self-discharge from an internal short, then vent gas, pressure and swelling, then a rising rate of temperature increase. Vehicle rules demand a warning to occupants at least five minutes before a hazard reaches the cabin, so detection cannot wait for heat.",
        "related": [
          "gas-detection",
          "internal-short-circuit",
          "off-gas",
          "un-r100-03",
          "thermal-runaway",
          "bms"
        ],
        "url": "https://lemonergy.com/learn/glossary/early-thermal-runaway-detection/",
        "mentions": [
          "self-discharge",
          "swelling"
        ]
      }
    },
    {
      "id": "term:electrolyte",
      "type": "Term",
      "label": "Electrolyte",
      "properties": {
        "id": "electrolyte",
        "name": "Electrolyte",
        "section": "topic-electrolytes",
        "definition": "The ion-conducting medium between the electrodes. In a liquid-electrolyte cell it fills the pores of both electrodes and the separator, so it is not a separate structural layer.",
        "related": [
          "lithium-salt",
          "carbonate-solvent",
          "electrolyte-additive",
          "ionic-conductivity",
          "solid-electrolyte",
          "ionic-liquid-electrolyte"
        ],
        "lesson": "fundamentals/cell-architecture/#electrolyte",
        "example": {
          "title": "Ions and electrons",
          "text": "Electrolyte carries ions between electrodes; the external circuit carries electrons. The two paths serve different roles."
        },
        "url": "https://lemonergy.com/learn/glossary/electrolyte/",
        "mentions": [
          "separator"
        ]
      }
    },
    {
      "id": "term:thermal-runaway",
      "type": "Term",
      "label": "Thermal runaway",
      "properties": {
        "id": "thermal-runaway",
        "name": "Thermal runaway",
        "section": "topic-safety",
        "definition": "Self-accelerating heating in a cell: heat speeds up reactions that release more heat, until the cell vents, catches fire or ruptures. An internal short, overcharge or external heating can trigger it.",
        "related": [
          "onset-temperature",
          "thermal-propagation",
          "venting",
          "separator-shutdown",
          "thermal-runaway-energy",
          "exothermic"
        ],
        "lesson": "fundamentals/cell-anatomy/#short-circuit",
        "url": "https://lemonergy.com/learn/glossary/thermal-runaway/",
        "mentions": [
          "overcharge"
        ]
      }
    }
  ]
}