☣️ UN 1079 • CLASS 2
Sulphur dioxide
Placard: Toxic Gas. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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Quick details
UN 1079
Class: 2
Placard type: Toxic Gas
ERG: Guide 125 (check current ERG)
Verify shipping papers and exact product details; use ERG Guide 125 for initial actions and isolation/evacuation guidance.
Chemical & Response Details
| Also known as | Sulfur dioxideSO2Sulfurous anhydrideSulfurous oxideSulfur oxide |
| CAS Number | 7446-09-5 |
| Appearance | Colorless gas with a pungent, suffocating odor similar to burnt matches. Shipped as a liquefied compressed gas under pressure. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | -10C (14F) |
| Vapor Density | 2.26 (heavier than air) |
| Water Reactivity | Reacts with water to form sulfurous acid (H2SO3), corrosive solution |
| Extinguishing | Not applicable - use water spray to reduce vapors, do not direct water at source |
| PPE | ⚠️ Level B minimum; SCBA required for any enclosed space or high concentration exposure; chemical-resistant suit for liquid contact |
| Isolation | ERG 125: isolate 150m (500 ft) all directions; evacuate 800m (0.5 mi) downwind if large spill or tank rupture |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin.
- Vapors are extremely irritating and corrosive.
- Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may cause environmental contamination.
- Some may burn but none ignite readily.
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Some of these materials may react violently with water.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Many gases are heavier than air and will spread along the ground and collect in low or confined areas
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
Copy / share note
MAYDAY / HAZMAT QUICK NOTE UN 1079 — Sulphur dioxide Class: 2 | Placard: Toxic Gas ERG: Guide 125 (check current ERG) FIRST ACTIONS: use SOP/SOG + ERG; stage upwind; isolate; deny entry; request Hazmat.
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FAQ
TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin. Vapors are extremely irritating and corrosive. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may cause environmental contamination. Some may burn but none ignite readily. Vapors from liquefied gas are initially heavier than air and spread along ground. Some of these materials may react violently with water.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum; SCBA required for any enclosed space or high concentration exposure; chemical-resistant suit for liquid contact
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 125 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.