☣️ UN 1833 • CLASS 8
Sulphurous acid
Placard: Corrosive. 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 1833
Class: 8
Placard type: Corrosive
ERG: Guide 154 (check current ERG)
Isolation: ERG 154: isolate spill 25-50m all directions; evacuate immediate area; avoid low areas where SO2 vapors collect
Chemical & Response Details
| Also known as | Sulfurous acidSulfur dioxide solutionSO2 in waterBisulfite solution |
| CAS Number | 7782-99-2 |
| Appearance | Colorless to pale yellow aqueous solution with a sharp, pungent sulfur dioxide odor. Exists only in solution, decomposes to release SO2 gas. |
| Flash Point | Not applicable (non-flammable aqueous solution) |
| Boiling Point | Approximately 100C (212F) with decomposition releasing SO2 |
| Vapor Density | Not applicable (aqueous solution) |
| Water Reactivity | Miscible with water; already an aqueous solution of sulfur dioxide |
| Extinguishing | Water spray to reduce vapors, neutralize with soda ash or lime |
| PPE | ⚠️ Level B minimum; SCBA required; full chemical-resistant suit, neoprene or butyl rubber gloves |
| Isolation | ERG 154: isolate spill 25-50m all directions; evacuate immediate area; avoid low areas where SO2 vapors collect |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
- Contact with molten substance may cause severe burns to skin and eyes.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.).
- Corrosives in contact with metals may evolve flammable hydrogen gas.
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.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- 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
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UN 1833 — Sulphurous acid HAZMAT RADIO NOTE — UN 1833
Product: Sulphurous acid
Class 8 / Corrosive / ERG 154
PPE: Level B minimum; SCBA required; full chemical-resistant suit, neoprene or butyl rubber gloves
ISOLATION: ERG 154: isolate spill 25-50m all directions; evacuate immediate area; avoid low areas where SO2 vapors collect
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 1833 — Sulphurous acid
Class: 8 | Placard: Corrosive | ERG Guide: 154
Appearance: Colorless to pale yellow aqueous solution with a sharp, pungent sulfur dioxide odor. Exists only in solution, decomposes to release SO2 gas.
Water Reactivity: Miscible with water; already an aqueous solution of sulfur dioxide
Extinguishing: Water spray to reduce vapors, neutralize with soda ash or lime
PPE: Level B minimum; SCBA required; full chemical-resistant suit, neoprene or butyl rubber gloves
Isolation: ERG 154: isolate spill 25-50m all directions; evacuate immediate area; avoid low areas where SO2 vapors collect
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
• Contact with molten substance may cause severe burns to skin and eyes.
• Avoid any skin contact.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/1833 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1833 Sulphurous acid Cls8 ERG154 | ERG 154: isolate spill 25-50m all directions; evacuate immediate area; avoid low | allfirefighter.com/hazmat/un/1833SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/1833
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FAQ
TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Corrosives in contact with metals may evolve flammable hydrogen gas.
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; full chemical-resistant suit, neoprene or butyl rubber gloves
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 154 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.