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pretty_name: "Gas group, temperature class and autoignition temperature by substance"
license: other
license_name: source-terms-cited
license_link: https://referencesource.org/hazardous-area-substance-classification/
language:
- en
tags:
- reference-data
- provenance
- referencesource-org
configs:
- config_name: default
data_files:
- split: train
path: data/records.jsonl
---
# Gas group, temperature class and autoignition temperature by substance
**Canonical, always-current version: https://referencesource.org/hazardous-area-substance-classification/**
Machine-readable: https://referencesource.org/hazardous-area-substance-classification/data.json — this mirror is a point-in-time copy.
- **Last verified:** 2026-08-06
- **Stale after:** 2028-08-05 (past this date, prefer the canonical copy —
it re-verifies on a cadence this snapshot does not)
- **Records:** 73
Hazardous area (explosive atmosphere) classification of individual flammable gases, vapours and combustible dusts. Each record is one substance as classified by one publisher, giving the apparatus / gas group (IIA, IIB, IIC, IIB+H2 under IEC 60079 and ATEX, or Class I Group A/B/C/D under the US National Electrical Code), the temperature class (T1 to T6), and the autoignition temperature the publisher prints. Answers 'is toluene IIA or IIB', 'what temperature class is acetone', 'MEK autoignition temperature for explosion proof equipment', 'NEC Group C equivalent IEC gas group', 'what gas group is hydrogen sulphide', and 'ethylene gas group and T class'. Publishers disagree on the autoignition temperature of the same substance -- hydrogen is printed as 500 C, 520 C and 560 C by three different manufacturers, and ethylene as 450 C and 490 C -- and because the temperature class is derived from that number the disagreement changes which equipment is legal to install. Every value is quoted from the page that printed it and attributed, so the disagreements are visible rather than averaged away.
## Provenance — what every record carries
Every record carries `source` (the URL the value was read from) and
`source_quote` (a verbatim quote from that page stating it). A value you
cannot check against its page is indistinguishable from an invented one;
these can all be checked. Each record is also individually addressable on
the canonical site at its `url`.
## Licence position
Facts extracted from freely published manufacturer and industry reference pages. Gas group and temperature class assignments are safety classifications and the underlying values are facts, not copyrightable expression. The authoritative documents (NFPA 497, IEC 60079-20-1) are not reproduced and were not opened -- the fact is taken, never the document. No bulk take from any single source: records come one or two substances at a time from five separate publishers.
Facts are not copyrightable; what this dataset takes from each source is a
fact plus a short attributed quote linking back to the page that states it.
## Sources
- https://www.e2s.com/guide-for-hazardous-areas/apparatus-groups-and-common-flammable-ga
- https://exknowledge.com/pages/gas-groups.html
- https://ldpi-inc.com/resources/classification-codes/class-1-locations/
- https://www.euroswitch.com/wp-content/uploads/euroswitch-hazardous-area-guide_V6.pdf
- https://greenishco.com/Downloads/ATEX.pdf
- https://www.cortemgroup.com/en/news/the-zones-of-the-plant-the-groups-and-the-temperature-classes-of-gases
## Fields
See any record in `data/records.jsonl` — field names are self-describing,
and the canonical page for each record renders them with labels:
https://referencesource.org/hazardous-area-substance-classification/
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