☣️ UN 1929 • CLASS 4
UN 1929 — Potassium hydrosulphite
Placard: Spontaneously Combustible. ERG Guide 135. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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.
Advertisement
UN 1929 Quick Details
UN 1929
Product name: Potassium hydrosulphite
DOT Class: 4
Placard type: Spontaneously Combustible
ERG Guide: 135 (check current ERG)
Initial isolation: ERG 135: Isolate spill 25-50m all directions. If fire or large spill, isolate 800m initial; protect downwind 1600m.
Common Hazards of UN 1929
- Flammable/combustible material.
- May ignite on contact with moist air or moisture.
- May burn rapidly with flare-burning effect.
- Some react vigorously or explosively on contact with water.
- Some may decompose explosively when heated or involved in a fire.
- May re-ignite after fire is extinguished.
- Runoff may create fire or explosion hazard.
- Containers may explode when heated.
Chemical Identity & Physical Properties
| Also known as | Potassium dithionitePotassium hyposulfiteDithionous acid dipotassium saltPotassium hydrosulfite |
| CAS Number | 14293-73-3 |
| Appearance | White to yellowish crystalline powder or granular solid. Odorless or slight sulfur dioxide odor when exposed to air. Decomposes and may ignite spontaneously when exposed to moisture. |
| Flash Point | Not applicable (spontaneously combustible solid when wet) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts with water releasing heat and sulfur dioxide gas. May ignite spontaneously when wet. Do not use water directly on material. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1929
Extinguishing Media
Dry sand, dry chemical, soda ash. DO NOT use water, foam, or CO2 directly on material.
PPE Requirements
⚠️ Level B minimum with SCBA required. Full protective clothing. Avoid contact with skin and eyes. Respiratory protection mandatory due to sulfur dioxide release.
Isolation & Evacuation
ERG 135: Isolate spill 25-50m all directions. If fire or large spill, isolate 800m initial; protect downwind 1600m.
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 135).
First Actions for a UN 1929 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Stay upwind, uphill and/or upstream.
- Keep unauthorized personnel away.
- 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
Advertisement
📋 Copy & Share Field Card
UN 1929 — Potassium hydrosulphiteHAZMAT RADIO NOTE — UN 1929
Product: Potassium hydrosulphite
Class 4 / Spontaneously Combustible / ERG 135
PPE: Level B minimum with SCBA required. Full protective clothing. Avoid contact with skin and eyes. Respiratory protection mandatory due to sulfur dioxide release.
ISOLATION: ERG 135: Isolate spill 25-50m all directions. If fire or large spill, isolate 800m initial; protect downwind 1600m.
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 1929 — Potassium hydrosulphite
Class: 4 | Placard: Spontaneously Combustible | ERG Guide: 135
Appearance: White to yellowish crystalline powder or granular solid. Odorless or slight sulfur dioxide odor when exposed to air. Decomposes and may ignite spontaneously when exposed to moisture.
Water Reactivity: Reacts with water releasing heat and sulfur dioxide gas. May ignite spontaneously when wet. Do not use water directly on material.
Extinguishing: Dry sand, dry chemical, soda ash. DO NOT use water, foam, or CO2 directly on material.
PPE: Level B minimum with SCBA required. Full protective clothing. Avoid contact with skin and eyes. Respiratory protection mandatory due to sulfur dioxide release.
Isolation: ERG 135: Isolate spill 25-50m all directions. If fire or large spill, isolate 800m initial; protect downwind 1600m.
— Key Hazards —
• Flammable/combustible material.
• May ignite on contact with moist air or moisture.
• May burn rapidly with flare-burning effect.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Stay upwind, uphill and/or upstream.
• Keep unauthorized personnel away.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/1929 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1929 Potassium hydrosulphite Cls4 ERG135 | allfirefighter.com/hazmat/un/1929SMS / 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/1929
Advertisement
Frequently Asked Questions about UN 1929
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Stay upwind, uphill and/or upstream. Keep unauthorized personnel away.
Level B minimum with SCBA required. Full protective clothing. Avoid contact with skin and eyes. Respiratory protection mandatory due to sulfur dioxide release.
Water reactivity: Reacts with water releasing heat and sulfur dioxide gas. May ignite spontaneously when wet. Do not use water directly on material.. Recommended extinguishing: Dry sand, dry chemical, soda ash. DO NOT use water, foam, or CO2 directly on material..
ERG Guide 135 recommendation: ERG 135: Isolate spill 25-50m all directions. If fire or large spill, isolate 800m initial; protect downwind 1600m.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 135 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.