UN 3148 — Water-reactive liquid, n.o.s.
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Water-reactive liquid, n.o.s. covers liquids that produce dangerous reactions with water. The exact product controls whether toxic gases, ignition or violent reaction is likely.
Hazard overview: A spill may spread as a liquid before water contact releases flammable gas and heat. Moisture, wet absorbent, rain or hose streams can worsen the incident.
Response guidance: Keep water away, isolate low areas and remove ignition sources. Use dry media only if compatible with the exact material and request hazmat technical support before close handling.
Firefighter training notes: Train responders to control runoff before it reaches dangerous-when-wet liquids. Do not use routine decon streams until the product has been identified.
Regulatory context: UN 3148 is a Class 4 dangerous-when-wet liquid entry. Verify packing group, subsidiary risks and exact composition from shipping papers and SDS.
Storage & handling: Store dry in tightly closed compatible containers, separated from water sources, acids, oxidizers and ignition sources. Protect from sprinkler discharge unless facility plans specify compatible controls.
UN 3148 Quick Details
Common Hazards of UN 3148
- Water-reactive liquid that can release flammable gas and heat on contact with water.
- May ignite from moisture, rain, wet absorbents or firefighting runoff.
- Some products under this n.o.s. entry may react violently with water or acids.
- Vapors or decomposition products may be toxic, corrosive or flammable depending on the chemical.
- Containers may rupture when heated or contaminated.
- Liquid can spread before reacting, increasing the fire area and exposure risk.
- Exact reactivity must be verified from SDS and shipping papers before applying any extinguishing media.
Chemical Identity & Physical Properties
Variable appearance depending on specific substance; typically clear to colored liquid that reacts with water or moisture in air. May emit visible fumes or heat upon contact with moisture Appearance and odor vary, so identify the liquid from container markings and shipping papers.
| Also known as | Water-reactive liquid not otherwise specifiedDangerous when wet liquidClass 4.3 liquidUN3148 |
| Appearance | Variable appearance depending on specific substance; typically clear to colored liquid that reacts with water or moisture in air. May emit visible fumes or heat upon contact with moisture. |
| Flash Point | Variable, substance-dependent; many have low flash points below 23C (73F) |
| Boiling Point | Variable, substance-dependent; typically 50-200C (122-392F) range |
| Vapor Density | Variable, substance-dependent; typically heavier than air (>1) |
| Water Reactivity | Reacts vigorously to violently with water, producing flammable gases (often hydrogen or other flammable vapors); may ignite spontaneously on contact with water or moist air |
Fireground Response Guidance — UN 3148
Extinguishing Media
PPE Requirements
Use SCBA and chemical-resistant protective clothing. Level A may be required if the identity is unknown or toxic gas release is possible.
Isolation & Evacuation
First Actions for a UN 3148 Incident
- Call 911 and the emergency response number shown on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command before close approach.
- Stay upwind, uphill and upstream; avoid low areas where vapors or gases may collect.
- Avoid breathing vapors, dust, mist or fire gases and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper PPE and training.
- Keep the material completely dry; do not add water, foam or wet absorbents to the release.
- Use ERG guidance, SDS, shipping papers and monitoring results for final protective actions.
📋 Copy & Share Field Card
UN 3148 — Water-reactive liquid, n.o.s.Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.