Substance profile
Hydrogen
Hydrogen is a colorless gas and is odorless.
01 · Identification
What Hydrogen is
Hydrogen is a colorless gas and is odorless. Its molecular formula is H2 and its molecular weight is 2.016 g/mol. It boils at -259 °C, melts at -253 °C.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 4th degree.
02 · Identifiers
Hydrogen identifiers and molecular data
Hydrogen CAS number and EC number
Hydrogen molecular formula and molecular weight
03 · GHS classification
Hydrogen hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Hydrogen pictograms and signal word
Hydrogen hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Flammable gases GHS chapter 2.2 | Category 1A | H220 | GHS02 |
Hydrogen hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H220 | Extremely flammable gas. |
This page lists only the codes assigned to Hydrogen. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Hydrogen
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Hydrogen issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Hydrogen precautionary statements
CLP Annex VI assigns 3 precautionary statements to Hydrogen. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Hydrogen name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | водород |
| Spanish español | Hidrógeno |
| Czech čeština | vodík |
| Danish dansk | hydrogen (brint) |
| German Deutsch | Wasserstoff |
| Estonian eesti | vesinik |
| Greek ελληνικά | υδρογόνο |
| English English | hydrogen |
| French français | hydrogène |
| Croatian hrvatski | vodik |
| Italian italiano | idrogeno |
| Latvian latviešu | ūdeņradis |
| Lithuanian lietuvių | vandenilis |
| Hungarian magyar | hidrogén |
| Maltese Malti | idroġenu |
| Dutch Nederlands | waterstof |
| Polish polski | wodór |
| Portuguese português | hidrogénio |
| Romanian română | hidrogen |
| Slovak slovenčina | vodík |
| Slovenian slovenščina | vodik |
| Finnish suomi | vety |
| Swedish svenska | väte |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Hydrogen GHS label elements
Everything CLP Annex VI fixes for Hydrogen, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Hydrogen
- Extremely flammable gas.
- Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
- Keep container tightly closed.
- Store in a well-ventilated place.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Hydrogen in the GHS label constructor →
07 · Health hazards
Hydrogen health hazards and exposure limits
Hydrogen hazard summary
Simple asphyxiant; Contact with evaporating liquid can cause frostbite; [HSDB]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
08 · Physical and chemical properties
Hydrogen properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Hydrogen boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -259.16 °C (-434.5 °F) | HSDB | |
| -252.78 °C (-423 °F) | at 760 mmHg | CAMEO |
Hydrogen melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -252.76 °C (-423 °F) | HSDB | |
| -258.89 °C (-434 °F) | CAMEO |
Hydrogen density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.0001 g/cm³ | HSDB | |
| 0.071 g/cm³ | at -253 °C | CAMEO |
Hydrogen solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Very low solubility in most liquids | HSDB | |
| In water, 1.62 mg/L at 21 °C | at 21 °C | HSDB | |
| Solubility in water, mg/l at 21 °C: 1.62 (very poor) | at 21 °C | ICSC |
Hydrogen vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 1240000 mmHg | at 25 °C | HSDB |
Hydrogen flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | Flammable gas | ICSC |
Hydrogen autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 500 °C (932 °F) | HSDB | |
| 573.89 °C (1065 °F) | CAMEO |
Hydrogen lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | 4 % by volume | HSDB | |
| 4.1 % by volume | HSDB |
Hydrogen upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | 75 % by volume | % by vol | HSDB |
| 74.2 % by volume | HSDB | ||
| 75 % by volume | CAMEO |
Hydrogen vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 0.07 (air = 1) | ICSC |
Hydrogen critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | -239.9 °C (-399.8 °F) | HSDB |
Hydrogen corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Noncorrosive | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Hydrogen fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Hydrogen fire potential
Highly dangerous fire and severe explosion hazard when exposed to heat, flame, or oxidizers.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Hydrogen storage and handling
Hydrogen safe storage
Fireproof. Cool. Ventilation along the floor and ceiling. Separated from oxidizing materials.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Hydrogen storage conditions
Store in a cool, dry, well-ventilated location. Outside or detached storage is preferred. Isolate from oxygen, halogens, other oxidizing materials. /Hydrogen, refrigerated liquid/
Source: Hazardous Substances Data Bank (HSDB)
Hydrogen incompatible materials
Release of hydrogen @ 47.5 bar into a vented 17.5-l chromium-plated sphere caused explosive ignition. /Hydrogen/
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Hydrogen in the storage compatibility matrix →
11 · Transport
Hydrogen UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
The same CAS number is shipped under more than one UN number. Which entry applies follows from the form and the concentration of the consignment — read the proper shipping name, not the CAS.
Hydrogen under UN 1049 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| HYDROGEN, COMPRESSED | 2 | 1F | — | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 2 is “Gases” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Hydrogen, compressed | 2.1 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.1 is “Flammable gas” (49 CFR 173.2).
Hydrogen under UN 1966 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| HYDROGEN, REFRIGERATED LIQUID | 2 | 3F | — | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 2 is “Gases” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Hydrogen, refrigerated liquid (cryogenic liquid) | 2.1 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.1 is “Flammable gas” (49 CFR 173.2).
12 · Questions
Hydrogen — frequently asked questions
What is the CAS number of Hydrogen?
The CAS number of Hydrogen is 1333-74-0. Its EC number is 215-605-7.
What is the chemical formula of Hydrogen?
The molecular formula of Hydrogen is H2 and its molecular weight is 2.016 g/mol.
What does a Hydrogen label have to show?
Under CLP Annex VI the label for Hydrogen carries the pictograms Flame and Gas cylinder and the signal word is Danger.
Is Hydrogen flammable?
Yes. CLP Annex VI assigns Hydrogen H220 — extremely flammable gas. The flash point reported for it is Flammable gas (ICSC).
Is Hydrogen a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Hydrogen. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the boiling point of Hydrogen?
The boiling point reported for Hydrogen is -259.16 °C (-434.5 °F) (HSDB).
What is the melting point of Hydrogen?
The melting point reported for Hydrogen is -252.76 °C (-423 °F) (HSDB).
How should Hydrogen be stored?
CLP Annex VI assigns Hydrogen the storage statement P403. Store in a cool, dry, well-ventilated location. Outside or detached storage is preferred. Isolate from oxygen, halogens, other oxidizing materials. /Hydrogen, refrigerated liquid/ (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Hydrogen
Keep going: substances starting with H, or search the whole database by name, CAS number, pictogram or signal word.