Substance profile
Sulfur Dioxide
Sulfur Dioxide is a colorless gas or liquid with a strong suffocating odor.
01 · Identification
What Sulfur Dioxide is
Sulfur Dioxide is a colorless gas or liquid with a strong suffocating odor. It boils at -10 °C, melts at -75.5 °C.
Under the GHS it carries the signal word Danger.
02 · Identifiers
Sulfur Dioxide identifiers and molecular data
Sulfur Dioxide CAS number and EC number
Other names for Sulfur Dioxide
- sulphur dioxide
03 · GHS classification
Sulfur Dioxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Sulfur Dioxide pictograms and signal word
Sulfur Dioxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Acute toxicity - inhalation GHS chapter 3.1 | Category 3 | H331 | GHS06 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
| Specific target organ toxicity - single exposure GHS chapter 3.8 | Category 1 | H370 | GHS08 |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Sulfur Dioxide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H331 | Toxic if inhaled. |
| H370 | Causes damage to organs <or state all organs affected, if known> <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H314 | Causes severe skin burns and eye damage. |
This page lists only the codes assigned to Sulfur Dioxide. 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 Sulfur Dioxide
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 Sulfur Dioxide 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
Sulfur Dioxide precautionary statements
CLP Annex VI assigns 7 precautionary statements to Sulfur Dioxide. 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.
Response
What to do once exposure, spillage or fire has already happened.
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
Sulfur Dioxide 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 | серен диоксид |
| Spanish español | Dióxido de azufre |
| Czech čeština | oxid siřičitý sulfurum-dioxid |
| Danish dansk | svovldioxid |
| German Deutsch | Schwefeldioxid |
| Estonian eesti | vääveldioksiid |
| Greek ελληνικά | διοξείδιο του θείου |
| English English | sulphur dioxide sulfur dioxide |
| French français | dioxyde de soufre anhydride sulfureux |
| Croatian hrvatski | sumporov dioksid, sumporov dioksid |
| Italian italiano | biossido di zolfo diossido di zolfo |
| Latvian latviešu | sēra dioksīds |
| Lithuanian lietuvių | sieros dioksidas |
| Hungarian magyar | kén-dioxid |
| Maltese Malti | diossidu tal-kubrit |
| Dutch Nederlands | zwaveldioxide |
| Polish polski | ditlenek siarki |
| Portuguese português | dióxido de enxofre |
| Romanian română | dioxid de sulf |
| Slovak slovenčina | oxid siričitý |
| Slovenian slovenščina | žveplov dioksid |
| Finnish suomi | rikkidioksidi |
| Swedish svenska | svaveldioxid, svaveldioxid |
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
Sulfur Dioxide GHS label elements
Everything CLP Annex VI fixes for Sulfur Dioxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Sulfur Dioxide
- Toxic if inhaled.
- Causes damage to organs <or state all organs affected, if known> <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Causes severe skin burns and eye damage.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Use only outdoors or in a well-ventilated area.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF INHALED:
- Immediately call a POISON CENTER/doctor/…
- Do NOT induce vomiting.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Sulfur Dioxide in the GHS label constructor →
07 · Health hazards
Sulfur Dioxide health hazards and exposure limits
Sulfur Dioxide hazard summary
Sulfur dioxide is a colorless gas with a pungent odor. It is a liquid when under pressure, and it dissolves in water very easily. Sulfur dioxide in the air comes mainly from activities such as the burning of coal and oil at power plants or from copper smelting. In nature, sulfur dioxide can be released to the air from volcanic eruptions.
Source: Agency for Toxic Substances and Disease Registry (ATSDR)
Sulfur Dioxide carcinogenicity classification
Evaluation: There is inadequate evidence for the carcinogenicity in humans of sulfur dioxide, sulfites, bisulfites and metabisulfites. There is limited evidence for the carcinogenicity in experimental animals of sulfur dioxide. There is inadequate evidence for the carcinogenicity in experimental animals of sulfites, bisulfites and metabisulfites. Overall evaluation: Sulfur dioxide, sulfites, bisulfites and metabisulfites are not classifiable as to their carcinogenicity to humans (Group 3).
Source: Hazardous Substances Data Bank (HSDB)
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
Sulfur Dioxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 5.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 5 ppm (13 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 5 ppm (13 mg/m3) See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 2 ppm (5 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | 5 ppm (13 mg/m³) | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3) | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 100 ppm (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 100.0 [ppm] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 100 ppm | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Sulfur Dioxide 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.
Sulfur Dioxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -10.05 °C (13.9 °F) | HSDB | |
| -10 °C (14 °F) | NIOSH | ||
| -10 °C (14 °F) | at 760 mmHg | CAMEO |
Sulfur Dioxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -75.5 °C (-103.9 °F) | HSDB | |
| -75.56 °C (-104 °F) | NIOSH | ||
| -72.72 °C (-98.9 °F) | CAMEO |
Sulfur Dioxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.0026 g/cm³ | HSDB | |
| 1.5 g/cm³ | liquid | HSDB | |
| 1.434 g/cm³ | CAMEO |
Sulfur Dioxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Soluble in water | HSDB | |
| Soluble in water ... forms sulfurous acid (H2SO3) | HSDB | ||
| In water, 1.07X10+5 mg/L at 21 °C | at 21 °C | HSDB |
Sulfur Dioxide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 2432 mmHg | NIOSH | |
| 2432 mmHg | at 20 °C | CAMEO | |
| 2475 mmHg | at 20 °C | ICSC |
Sulfur Dioxide autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | Not flammable (USCG, 1999) | CAMEO |
Sulfur Dioxide lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Nonflammable Gas | NIOSH |
Sulfur Dioxide vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 2.26 (air = 1) | CAMEO | |
| 2.25 (air = 1) | ICSC |
Sulfur Dioxide odor threshold
| Property | Value | Conditions | Source |
|---|---|---|---|
| Odor threshold | 4.70X10-1 ppm (recognition in air, chemically pure) | HSDB | |
| Odor threshold: 0.1 ppm (low); 3.0 ppm (high) | HSDB | ||
| Odor threshold: 1.1750 mg/cu m (low); 12.5000 mg/cu m (high); Irritating odor concn: 5.0 mg/cu m. | HSDB |
Sulfur Dioxide critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 157.49 °C (315.5 °F) | HSDB |
Sulfur Dioxide corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Liquid sulfur dioxide will attack some forms of plastic, rubber, and coatings | HSDB | |
| Corrodes aluminum | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Sulfur Dioxide 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.
Sulfur Dioxide fire potential
Not combustible. /Sulfur dioxide, liquefied/
Source: Hazardous Substances Data Bank (HSDB)
Corrosivity
Iron, steel, nickel, copper-nickel alloys, & inconel nickel-chromium-iron are satisfactory for dry or hot sulfur dioxide, but they are readily corroded below the dew point or by wet sulfur dioxide gas. Liquid sulfur dioxide produces serious corrosion of iron, brass, and copper at about 0.2 wt% or higher moisture content.
Source: HSDB
10 · Handling and storage
Sulfur Dioxide storage and handling
Sulfur Dioxide safe storage
Ventilation along the floor. Dry.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Sulfur Dioxide storage conditions
Storage temp: less than 130 °F
Source: Hazardous Substances Data Bank (HSDB)
Sulfur Dioxide incompatible materials
Will react with water or steam to produce toxic and corrosive fumes.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Sulfur Dioxide in the storage compatibility matrix →
11 · Transport
Sulfur Dioxide 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.
Sulfur Dioxide under UN 1079 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| SULPHUR DIOXIDE | 2 | 2TC | — | |
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) |
|---|---|---|---|
| Sulfur dioxide | 2.3 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.3 is “Poisonous gas” (49 CFR 173.2).
12 · Questions
Sulfur Dioxide — frequently asked questions
What is the CAS number of Sulfur Dioxide?
The CAS number of Sulfur Dioxide is 7446-09-5. Its EC number is 231-195-2.
What does a Sulfur Dioxide label have to show?
Under CLP Annex VI the label for Sulfur Dioxide carries the pictograms Gas cylinder, Skull and crossbones, Health hazard and Corrosion and the signal word is Danger.
Is Sulfur Dioxide flammable?
CLP Annex VI assigns Sulfur Dioxide no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Sulfur Dioxide a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Sulfur Dioxide. 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. IARC places it in Group 3: not classifiable as to its carcinogenicity to humans.
What is the exposure limit for Sulfur Dioxide?
The US occupational exposure limit reported for Sulfur Dioxide is 5.0 [ppm] (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Sulfur Dioxide?
The boiling point reported for Sulfur Dioxide is -10.05 °C (13.9 °F) (HSDB).
What is the melting point of Sulfur Dioxide?
The melting point reported for Sulfur Dioxide is -75.5 °C (-103.9 °F) (HSDB).
How should Sulfur Dioxide be stored?
Storage temp: less than 130 °F (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Sulfur Dioxide
Keep going: substances starting with S, or search the whole database by name, CAS number, pictogram or signal word.