☣️ UN 3129 • CLASS 4
UN 3129 — Water-reactive liquid, corrosive, n.o.s.
Placard: Dangerous When Wet. ERG Guide 138. 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 3129 Quick Details
UN 3129
Product name: Water-reactive liquid, corrosive, n.o.s.
DOT Class: 4
Placard type: Dangerous When Wet
ERG Guide: 138 (check current ERG)
Initial isolation: ERG 138: Initial isolation 50m in all directions. Protective action distance: Small spill (drum) 100m downwind daytime, 200m night. Large spill 300m downwind daytime, 800m night. Evacuate spill and fire area as posted.
Common Hazards of UN 3129
- Produce flammable 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.
- Runoff may create fire or explosion hazard.
- Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
Chemical Identity & Physical Properties
| Also known as | Water-reactive corrosive liquid NOSCorrosive liquid which in contact with water emits flammable gasesWater-reactive corrosive substance liquid |
| Appearance | Variable appearance depending on specific substance. Typically a corrosive liquid that reacts with water or moisture to produce flammable gases. May be colorless to dark colored with irritating or pungent odor. |
| Flash Point | Not applicable (produces flammable gases on water contact) |
| Boiling Point | Variable depending on specific substance |
| Vapor Density | Variable, typically heavier than air |
| Water Reactivity | Reacts vigorously or explosively with water producing flammable and potentially toxic gases. Do not use water or aqueous agents for fire control. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3129
Extinguishing Media
Dry chemical, dry sand, or dry powder only. Do not use water, foam, or aqueous agents.
PPE Requirements
⚠️ Level A or B required. Full protective clothing, chemical-resistant suit, SCBA mandatory. Avoid contact with water or moisture during response operations.
Isolation & Evacuation
ERG 138: Initial isolation 50m in all directions. Protective action distance: Small spill (drum) 100m downwind daytime, 200m night. Large spill 300m downwind daytime, 800m night. Evacuate spill and fire area as posted.
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 138).
First Actions for a UN 3129 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
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
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UN 3129 — Water-reactive liquid, corrosive, n.o.s.HAZMAT RADIO NOTE — UN 3129
Product: Water-reactive liquid, corrosive, n.o.s.
Class 4 / Dangerous When Wet / ERG 138
PPE: Level A or B required. Full protective clothing, chemical-resistant suit, SCBA mandatory. Avoid contact with water or moisture during response operations.
ISOLATION: ERG 138: Initial isolation 50m in all directions. Protective action distance: Small spill (drum) 100m downwind daytime, 200m night. Large spill 300m downwind daytime, 800m night. Evacuate spill and fire area as posted.
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 3129 — Water-reactive liquid, corrosive, n.o.s.
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Variable appearance depending on specific substance. Typically a corrosive liquid that reacts with water or moisture to produce flammable gases. May be colorless to dark colored with irritating or pungent odor.
Water Reactivity: Reacts vigorously or explosively with water producing flammable and potentially toxic gases. Do not use water or aqueous agents for fire control.
Extinguishing: Dry chemical, dry sand, or dry powder only. Do not use water, foam, or aqueous agents.
PPE: Level A or B required. Full protective clothing, chemical-resistant suit, SCBA mandatory. Avoid contact with water or moisture during response operations.
Isolation: ERG 138: Initial isolation 50m in all directions. Protective action distance: Small spill (drum) 100m downwind daytime, 200m night. Large spill 300m downwind daytime, 800m night. Evacuate spill and fire area as posted.
— Key Hazards —
• Produce flammable 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/3129 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3129 Water-reactive liquid, corrosive, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/3129SMS / 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/3129
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Frequently Asked Questions about UN 3129
Produce flammable 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. Runoff may create fire or explosion hazard. Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
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 B required. Full protective clothing, chemical-resistant suit, SCBA mandatory. Avoid contact with water or moisture during response operations.
Water reactivity: Reacts vigorously or explosively with water producing flammable and potentially toxic gases. Do not use water or aqueous agents for fire control.. Recommended extinguishing: Dry chemical, dry sand, or dry powder only. Do not use water, foam, or aqueous agents..
ERG Guide 138 recommendation: ERG 138: Initial isolation 50m in all directions. Protective action distance: Small spill (drum) 100m downwind daytime, 200m night. Large spill 300m downwind daytime, 800m night. Evacuate spill and fire area as posted.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 138 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.