☣️ UN 3123 • CLASS 6
UN 3123 — Poisonous liquid, waterreactive, 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 3123 Quick Details
UN 3123
Product name: Poisonous liquid, waterreactive, n.o.s.
DOT Class: 6
Placard type: Toxic
ERG Guide: 139 (check current ERG)
Initial isolation: ERG 139: Isolate spill area immediately for at least 50-100 meters in all directions; evacuate downwind areas if gases evolving; keep unauthorized personnel away; consider evacuation of 800+ meters downwind if large spill or fire
Common Hazards of UN 3123
- 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 | Toxic liquid water-reactive NOSPoisonous liquid water-reactive not otherwise specifiedWater-reactive toxic liquid |
| Appearance | Appearance varies depending on specific substance; typically a liquid at room temperature. May be colorless to dark colored. Odor varies by specific chemical identity. |
| Flash Point | Varies by specific substance; many are highly flammable or may ignite spontaneously on contact with water |
| Boiling Point | Varies by specific substance; data dependent on chemical identity |
| Vapor Density | Typically heavier than air; specific value depends on substance identity |
| Water Reactivity | Reacts with water producing flammable and toxic gases; some react vigorously or explosively; DO NOT use water except to keep containers cool from a distance |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3123
Extinguishing Media
Dry chemical, dry sand, or other dry agents; DO NOT use water, foam, or water-based extinguishing agents due to violent reaction
PPE Requirements
⚠️ Level A or Level B with SCBA required; full chemical protective suit; avoid all contact; respiratory protection mandatory due to toxic gas generation
Isolation & Evacuation
ERG 139: Isolate spill area immediately for at least 50-100 meters in all directions; evacuate downwind areas if gases evolving; keep unauthorized personnel away; consider evacuation of 800+ meters downwind if large spill or fire
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 139).
First Actions for a UN 3123 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 3123 — Poisonous liquid, waterreactive, n.o.s.HAZMAT RADIO NOTE — UN 3123
Product: Poisonous liquid, waterreactive, n.o.s.
Class 6 / Toxic / ERG 139
PPE: Level A or Level B with SCBA required; full chemical protective suit; avoid all contact; respiratory protection mandatory due to toxic gas generation
ISOLATION: ERG 139: Isolate spill area immediately for at least 50-100 meters in all directions; evacuate downwind areas if gases evolving; keep unauthorized personnel away; consider evacuation of 800+ meters downwind if large spill or fire
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 3123 — Poisonous liquid, waterreactive, n.o.s.
Class: 6 | Placard: Toxic | ERG Guide: 139
Appearance: Appearance varies depending on specific substance; typically a liquid at room temperature. May be colorless to dark colored. Odor varies by specific chemical identity.
Water Reactivity: Reacts with water producing flammable and toxic gases; some react vigorously or explosively; DO NOT use water except to keep containers cool from a distance
Extinguishing: Dry chemical, dry sand, or other dry agents; DO NOT use water, foam, or water-based extinguishing agents due to violent reaction
PPE: Level A or Level B with SCBA required; full chemical protective suit; avoid all contact; respiratory protection mandatory due to toxic gas generation
Isolation: ERG 139: Isolate spill area immediately for at least 50-100 meters in all directions; evacuate downwind areas if gases evolving; keep unauthorized personnel away; consider evacuation of 800+ meters downwind if large spill or fire
— 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/3123 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3123 Poisonous liquid, waterreactive, n.o.s. Cls6 ERG139 | allfirefighter.com/hazmat/un/3123SMS / 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/3123
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Frequently Asked Questions about UN 3123
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 or Level B with SCBA required; full chemical protective suit; avoid all contact; respiratory protection mandatory due to toxic gas generation
Water reactivity: Reacts with water producing flammable and toxic gases; some react vigorously or explosively; DO NOT use water except to keep containers cool from a distance. Recommended extinguishing: Dry chemical, dry sand, or other dry agents; DO NOT use water, foam, or water-based extinguishing agents due to violent reaction.
ERG Guide 139 recommendation: ERG 139: Isolate spill area immediately for at least 50-100 meters in all directions; evacuate downwind areas if gases evolving; keep unauthorized personnel away; consider evacuation of 800+ meters downwind if large spill or fire
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.