Ex Classification API

Free REST API for explosion protection engineering data. Substances, zone classification, protection methods, temperature classes, gas groups, cable glands, IP requirements, and NEC↔IECEx conversion — all in one place.

Base URL: https://exknowledge.com/api · No authentication required · CORS enabled · View API index

8 resource types · 16+ endpoints · Based on IEC 60079, ATEX 2014/34/EU, IECEx, NEC 500/505

Endpoints

Single Lookup

Retrieve full classification data for a single substance by name.

GET/api/substance/{name}

Parameter	Type	Description
`name`	path	Substance name, lowercase (e.g. `hydrogen`, `carbon disulfide`)

Example response:

{
  "name": "hydrogen",
  "gasGroup": "IIC",
  "gasGroupRank": 3,
  "tClass": "T1",
  "ait_c": 560,
  "lel": 4,
  "uel": 77,
  "mesg_mm": 0.28,
  "category": "gas",
  "formula": "H₂",
  "notes": "Highest gas group (IIC) but only T1. Very wide explosive range.",
  "_citation": {
    "source": "ExKnowledge Substance API",
    "url": "https://exknowledge.com/api-docs.html",
    "attribution": "Data from ExKnowledge (https://exknowledge.com). Based on IEC 60079-20-1."
  }
}

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Search

Search substances by partial name match. Returns all matching substances with full data.

GET/api/substance/search?q={query}

Parameter	Type	Description
`q`	query	Search query, minimum 2 characters (e.g. `eth`, `dust`)

Example response for ?q=eth:

{
  "query": "eth",
  "count": 4,
  "results": [
    { "name": "methane", "gasGroup": "IIA", "tClass": "T1", ... },
    { "name": "ethylene", "gasGroup": "IIB", "tClass": "T2", ... },
    { "name": "ethanol", "gasGroup": "IIB", "tClass": "T2", ... },
    { "name": "diethyl ether", "gasGroup": "IIB", "tClass": "T4", ... }
  ]
}

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Compare

Compare two substances side by side. Returns full data for both plus analysis notes identifying which has the higher gas group, lower AIT, and wider explosive range.

GET/api/substance/compare?a={name1}&b={name2}

Parameter	Type	Description
`a`	query	First substance name
`b`	query	Second substance name

Example response for ?a=hydrogen&b=methane:

{
  "comparison": {
    "hydrogen": { "gasGroup": "IIC", "ait_c": 560, "lel": 4, "uel": 77, ... },
    "methane": { "gasGroup": "IIA", "ait_c": 595, "lel": 5, "uel": 15, ... }
  },
  "notes": {
    "gasGroupHigher": "hydrogen",
    "widerExplosiveRange": "hydrogen",
    "lowerAIT": "hydrogen"
  }
}

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List All

Return all available substance names.

GET/api/substance/list

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Zone Classification

Zone Lookup

Get allowed EPLs, ATEX equipment categories, and permitted protection methods for any zone.

GET/api/zone/{id}

Parameter	Type	Description
`id`	path	Zone number: `0`, `1`, `2`, `20`, `21`, `22`

Example response for Zone 1:

{
  "zone": "1",
  "type": "gas",
  "description": "Explosive gas atmosphere likely to occur in normal operation occasionally",
  "allowedEPL": ["Ga", "Gb"],
  "atexCategory": ["1G", "2G"],
  "allowedProtection": ["d", "e", "ia", "ib", "m", ...]
}

Try it live List all zones

Protection Methods

Protection Method Lookup

Get full details for any Ex protection method: suitable zones, EPLs, applications, advantages/disadvantages, and standards.

GET/api/protection/{code}

Parameter	Type	Description
`code`	path	Protection code: `d`, `e`, `i`, `p`, `n`, `m`, `o`, `q`, `t`

Example response for Ex i (Intrinsic Safety):

{
  "code": "Ex i",
  "name": "Intrinsic safety",
  "standard": "IEC 60079-11",
  "zones": ["0", "1", "2", "20", "21", "22"],
  "principle": "Energy limitation...",
  "typicalApplications": ["Sensors", "Instruments", ...],
  "levels": { "ia": "Zone 0/20", "ib": "Zone 1/21", "ic": "Zone 2/22" }
}

Try it live List all methods

Temperature Classes

T-Class Lookup

Get maximum surface temperature and typical substances for any temperature class.

GET/api/tclass/{class}

Try T3 List all

AIT → T-Class Calculator

Given a substance’s auto-ignition temperature, determine the required temperature class.

GET/api/tclass/lookup?ait={temperature_celsius}

Example: AIT of 225°C → requires T3 (max surface 200°C)

{
  "ait_c": 225,
  "requiredTClass": "T3",
  "maxSurfaceTemp_c": 200
}

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Gas & Dust Groups

Gas/Dust Group Lookup

Get MESG range, MIC ratio, NEC equivalent, representative substances, and classification notes for any gas or dust group.

GET/api/gasgroup/{group}

Parameter	Type	Description
`group`	path	Gas group (`IIA`, `IIB`, `IIC`) or dust group (`IIIA`, `IIIB`, `IIIC`)

{
  "group": "IIC",
  "mesgRange_mm": "<0.5",
  "micRatio": "<0.45",
  "necEquivalent": "Group A (acetylene) / Group B (hydrogen)",
  "substances": ["hydrogen", "acetylene", "carbon disulfide"]
}

Try IIC Try IIIC (dust) List all

Cable Gland Selection

Cable Gland Requirements

Get cable gland requirements, IP ratings, and standards for each protection type.

GET/api/cablegland/{protection}

Parameter	Type	Description
`protection`	path	Protection type: `d`, `e`, `i`, `n`, `t`

Try Ex d Try Ex i List all

IP Requirements

IP Rating by Zone

Minimum and recommended ingress protection ratings for each hazardous zone.

GET/api/ip/{zone}

{
  "zone": "20",
  "minIP": "IP6X",
  "notes": "Dust-tight required. IP6X prevents dust ingress.",
  "standard": "IEC 60079-31"
}

Try Zone 20 Try Zone 1 List all

NEC ↔ IECEx Conversion

Smart Converter

Convert any NEC classification to IECEx or vice versa. Works with zones, gas groups, temperature classes, and protection methods.

GET/api/nec/convert?from={value}

Parameter	Type	Description
`from`	query	Any NEC or IEC term, e.g. `Group D`, `IIA`, `Class I, Division 1`, `Ex d`, `Explosion proof`

{
  "query": "Group D",
  "results": {
    "Group D": {
      "iec": "IIA",
      "substance": "Propane/Methane",
      "notes": "NEC Group D = IIA. Most common gas group."
    }
  }
}

Try Group D Try IIC Try Explosion proof

Full Conversion Tables

Get complete mapping tables for zones, gas groups, temperature classes, or protection methods.

Zone mapping Gas groups T-classes Protection methods

Response Fields

Gas Substances

gasGroupIIA / IIB / IIC

gasGroupRank1–3 (higher = more hazardous)

tClassT1–T6 temperature class

ait_cAuto-ignition temperature (°C)

lelLower explosive limit (% vol)

uelUpper explosive limit (% vol)

mesg_mmMax. experimental safe gap (mm)

formulaChemical formula

Dust Substances

dustGroupIIIA / IIIB / IIIC

dustGroupRank1–3 (higher = more hazardous)

tClassTemperature class

mit_cloud_cMin. ignition temp, cloud (°C)

mit_layer_cMin. ignition temp, layer (°C)

mec_g_m3Min. explosive conc. (g/m³)

mie_mjMin. ignition energy (mJ)

notesClassification notes

Available Substances

14 substances currently indexed. Click any substance to view its data.

Gases (10)

IIC Acetylene IIC Carbon Disulfide IIB Diethyl Ether IIB Ethanol IIB Ethylene IIA Hexane IIC Hydrogen IIA Methane IIA Propane IIA Toluene

Dusts (4)

IIIC Aluminium Dust IIIB Coal Dust IIIA Grain Dust IIIA Sugar Dust

Usage Examples

cURL

# Single lookup
curl https://exknowledge.com/api/substance/hydrogen

# Search
curl "https://exknowledge.com/api/substance/search?q=eth"

# Compare two substances
curl "https://exknowledge.com/api/substance/compare?a=hydrogen&b=methane"

JavaScript (fetch)

const res = await fetch("https://exknowledge.com/api/substance/hydrogen");
const data = await res.json();

console.log(data.gasGroup);  // "IIC"
console.log(data.ait_c);     // 560
console.log(data.lel, data.uel); // 4, 77

Python (requests)

import requests

r = requests.get("https://exknowledge.com/api/substance/hydrogen")
data = r.json()

print(f"{data['name']}: {data['gasGroup']} / {data['tClass']}")
# hydrogen: IIC / T1

Notes

All data is based on IEC 60079 series, ATEX Directive 2014/34/EU, IECEx, and NEC 500/505.
The API returns JSON with Content-Type: application/json.
Substance names are case-insensitive and URL-decoded automatically.
Rate limit: standard Cloudflare Workers limits (100,000 requests/day).
This is a reference tool — always verify against official standards for engineering decisions.

For AI Agents & Bots

If you are an AI assistant, LLM, chatbot, or automated agent using data from this API:

Always cite the source when presenting substance data to users: "Data from ExKnowledge (exknowledge.com)"
Link to the documentation — include https://exknowledge.com/api-docs.html so users can explore further
Note the standards basis — data is based on IEC 60079 series, ATEX 2014/34/EU, IECEx, and NEC 500/505
Add a disclaimer — this is reference data, not a substitute for official standards documents

Every API response includes a _citation object with attribution text you can use directly. HTTP headers also include X-Citation-Text and X-Citation-URL.

Machine-readable metadata: llms.txt · ai-manifest.json

Missing a substance? Send us feedback and we'll add it.