☣️ 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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⚠️ Verification required:
Broad or variable material category; verify exact product, SDS and shipping papers.
⚠️ 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.
Water-reactive liquid, corrosive, n.o.s. is a broad n.o.s. hazmat entry. The material family gives important initial clues, but responders must confirm the exact product, concentration and packaging from shipping papers and the SDS.
Hazard overview: Treat this entry as variable and product-specific. Main concerns include toxic exposure, fire or reaction hazards, container failure when heated, and incompatible contact with water, air, fuels or metals depending on the exact substance.
Response guidance: Set isolation, keep responders upwind and avoid direct contact. Do not apply water or foam to water-reactive material unless compatibility is confirmed. Use ERG guidance first, then refine with SDS, shipping papers and monitoring.
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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: Use ERG 138 as initial guidance, then adjust isolation using SDS, shipping papers, monitoring data, wind and package condition.
Common Hazards of UN 3129
- Reacts with water or moisture; reaction may be vigorous or explosive depending on the exact product.
- Water contact may release flammable, toxic and/or corrosive gases that can collect in low or confined areas.
- May ignite on contact with water, humid air or contaminated absorbents.
- Corrosive to skin, eyes and some metals; contact with metals may generate flammable hydrogen gas.
- Containers may rupture or explode when heated.
- Fire may produce irritating, toxic or corrosive smoke and runoff.
- Because this is an n.o.s. entry, the SDS and shipping papers define the exact hazards and response limits.
Chemical Identity & Physical Properties
Physical appearance is product-specific. This entry covers liquid materials that may vary in color, odor, concentration and packaging, so visual identification alone is not reliable.
| 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 | Water-reactive n.o.s. material; reaction severity depends on the exact product. Keep dry and verify SDS before any water use. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3129
Extinguishing Media
Use dry chemical, dry sand, dry earth, soda ash or lime as appropriate. Do not use water or foam directly unless SDS confirms compatibility.
PPE Requirements
⚠️ SCBA and chemical-resistant protection required. Use Level A for unknown identity, active gas release or major spill; Level B only when monitoring supports it.
Use SCBA and chemical-resistant protection. Level A is preferred for unknown identity, vapor/gas release or major spill; Level B may be used only with monitoring and command approval.
Isolation & Evacuation
Use ERG 138 as initial guidance, then adjust isolation using SDS, shipping papers, monitoring data, wind and package condition.
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 and the emergency response number shown on shipping papers.
- Keep unauthorized personnel away and establish an isolation zone.
- Stay upwind, uphill and upstream; avoid low areas where vapors or gases may collect.
- Avoid breathing vapors, dust, smoke or decomposition gases and avoid skin or eye contact.
- Do not touch damaged packages, containers or spilled material without proper PPE.
- Ventilate confined spaces only if responders are trained, equipped and monitoring the atmosphere.
- Keep water away from the material unless SDS or incident command confirms it is safe for cooling containers.
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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: SCBA and chemical-resistant protection required. Use Level A for unknown identity, active gas release or major spill; Level B only when monitoring supports it.
ISOLATION: Use ERG 138 as initial guidance, then adjust isolation using SDS, shipping papers, monitoring data, wind and package condition.
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: Water-reactive n.o.s. material; reaction severity depends on the exact product. Keep dry and verify SDS before any water use.
Extinguishing: Use dry chemical, dry sand, dry earth, soda ash or lime as appropriate. Do not use water or foam directly unless SDS confirms compatibility.
PPE: SCBA and chemical-resistant protection required. Use Level A for unknown identity, active gas release or major spill; Level B only when monitoring supports it.
Isolation: Use ERG 138 as initial guidance, then adjust isolation using SDS, shipping papers, monitoring data, wind and package condition.
— Key Hazards —
• Reacts with water or moisture; reaction may be vigorous or explosive depending on the exact product.
• Water contact may release flammable, toxic and/or corrosive gases that can collect in low or confined areas.
• May ignite on contact with water, humid air or contaminated absorbents.
— First Actions —
• Call 911 and the emergency response number shown on shipping papers.
• Keep unauthorized personnel away and establish an isolation zone.
• Stay upwind, uphill and upstream; avoid low areas where vapors or gases may collect.
• Avoid breathing vapors, dust, smoke or decomposition gases and avoid skin or eye contact.
SOURCE: allfirefighter.com/hazmat/un/water-reactive-liquid-corrosive-un-3129 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3129 Water-reactive liquid, corrosive, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/water-reactive-liquid-corrosive-un-3129SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/water-reactive-liquid-corrosive-un-3129
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Frequently Asked Questions about UN 3129
It covers a broad n.o.s. liquid category. The exact chemical, concentration and additives must be confirmed from the SDS and shipping papers.
The entry is broad or variable, so one fixed behavior cannot be assumed for every shipment.
For water-reactive entries, yes; moisture may release flammable, toxic or corrosive gases. Keep material dry unless SDS confirms water is safe.
SCBA and chemical-resistant clothing are needed. Use Level A for unknown products, active vapor/gas release or major spills.
Check shipping papers, SDS, package markings, wind direction and atmospheric monitoring before committing crews.
Yes. Heat can rupture containers and may intensify reaction, toxic release or fire spread depending on the product.
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.