☣️ UN 3125 • CLASS 6
UN 3125 — Poisonous solid, water-reactive, n.o.s.
Placard: Toxic. ERG Guide 139. 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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UN 3125 Quick Details
UN 3125
Product name: Poisonous solid, water-reactive, n.o.s.
DOT Class: 6
Placard type: Toxic
ERG Guide: 139 (check current ERG)
Initial isolation: ERG 139: isolate spill area 25-50m all directions; if fire or water contact occurs, increase isolation to 800m and consider evacuation 1600m downwind
Common Hazards of UN 3125
- Produce flammable and toxic gases on contact with water.
- May ignite on contact with water or moist air.
- Some react vigorously or explosively on contact with water.
- May be ignited by heat, sparks or flames.
- May re-ignite after fire is extinguished.
- Some are transported in highly flammable liquids.
- Containers may explode when heated.
- Runoff may create fire or explosion hazard.
Chemical Identity & Physical Properties
| Also known as | Water-reactive toxic solid n.o.s.Toxic water-reactive solidPoisonous water-reactive solid not otherwise specifiedUN3125 |
| Appearance | Variable appearance depending on specific substance; typically a solid material that produces toxic and flammable gases upon contact with water or moisture. Physical state is solid at room temperature. |
| Flash Point | Not applicable (water-reactive solid) |
| Boiling Point | Not applicable (decomposes or reacts with moisture) |
| Vapor Density | Not applicable (solid, but produces toxic/flammable gases on water contact) |
| Water Reactivity | Reacts violently with water producing flammable and toxic gases; may ignite spontaneously on contact with water or moist air |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3125
Extinguishing Media
Dry chemical, dry sand, or dry lime only; DO NOT use water, foam, or CO2
PPE Requirements
⚠️ Level A recommended; SCBA required; full chemical-resistant suit; avoid all water contact; ensure respiratory protection from toxic gas generation
Isolation & Evacuation
ERG 139: isolate spill area 25-50m all directions; if fire or water contact occurs, increase isolation to 800m and consider evacuation 1600m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 139).
First Actions for a UN 3125 Incident
- 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 3125 — Poisonous solid, water-reactive, n.o.s.HAZMAT RADIO NOTE — UN 3125
Product: Poisonous solid, water-reactive, n.o.s.
Class 6 / Toxic / ERG 139
PPE: Level A recommended; SCBA required; full chemical-resistant suit; avoid all water contact; ensure respiratory protection from toxic gas generation
ISOLATION: ERG 139: isolate spill area 25-50m all directions; if fire or water contact occurs, increase isolation to 800m and consider evacuation 1600m downwind
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 3125 — Poisonous solid, water-reactive, n.o.s.
Class: 6 | Placard: Toxic | ERG Guide: 139
Appearance: Variable appearance depending on specific substance; typically a solid material that produces toxic and flammable gases upon contact with water or moisture. Physical state is solid at room temperature.
Water Reactivity: Reacts violently with water producing flammable and toxic gases; may ignite spontaneously on contact with water or moist air
Extinguishing: Dry chemical, dry sand, or dry lime only; DO NOT use water, foam, or CO2
PPE: Level A recommended; SCBA required; full chemical-resistant suit; avoid all water contact; ensure respiratory protection from toxic gas generation
Isolation: ERG 139: isolate spill area 25-50m all directions; if fire or water contact occurs, increase isolation to 800m and consider evacuation 1600m downwind
— Key Hazards —
• Produce flammable and toxic gases on contact with water.
• May ignite on contact with water or moist air.
• Some react vigorously or explosively on contact with water.
— 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/3125 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3125 Poisonous solid, water-reactive, n.o.s. Cls6 ERG139 | allfirefighter.com/hazmat/un/3125SMS / 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/3125
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Frequently Asked Questions about UN 3125
Produce flammable and toxic gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Containers may explode when heated. Runoff may create fire or explosion hazard.
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 A recommended; SCBA required; full chemical-resistant suit; avoid all water contact; ensure respiratory protection from toxic gas generation
Water reactivity: Reacts violently with water producing flammable and toxic gases; may ignite spontaneously on contact with water or moist air. Recommended extinguishing: Dry chemical, dry sand, or dry lime only; DO NOT use water, foam, or CO2.
ERG Guide 139 recommendation: ERG 139: isolate spill area 25-50m all directions; if fire or water contact occurs, increase isolation to 800m and consider evacuation 1600m downwind
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 139 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.