UN 3133 — Water-reactive solid, oxidizing, 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 solid, oxidizing, n.o.s. is a dangerous-when-wet entry for solids that can generate flammable gas when exposed to water. Because it is n.o.s., responders must confirm the exact product from the SDS and shipping papers.
Hazard overview: Water-reactive solid, oxidizing, n.o.s. can react with water, humidity or wet firefighting runoff to release flammable gas and heat. Some products may ignite, re-ignite or react violently, so responders should treat unknown material as unstable until identified.
Response guidance: Keep the release dry, isolate the area and remove ignition sources. Use dry sand, dry chemical or other product-approved dry media from a safe distance; do not use water, foam or wet absorbent unless a hazmat specialist confirms compatibility.
Firefighter training notes: Train responders to recognize dangerous-when-wet placards, keep hose streams and decon runoff away from the product, and request hazmat resources early. A common error is applying water before the chemical identity is confirmed.
Regulatory context: UN 3133 is a Class 4 dangerous-when-wet shipping entry. The exact proper shipping name, subsidiary risks, packing group and reportable requirements must be verified from the shipping papers and SDS.
Storage & handling: Store sealed containers in a dry, well-ventilated area away from water, humidity, acids, oxidizers and ignition sources. Keep incompatible firefighting media and wet absorbents away from the storage location.
UN 3133 Quick Details
Common Hazards of UN 3133
- Produces flammable gas when exposed to water or moist air.
- May ignite spontaneously on contact with moisture.
- Some materials under this n.o.s. entry may react violently or explosively with water.
- It combines dangerous-when-wet behavior with oxidizing properties that can intensify nearby fires.
- Heat, friction or contamination may increase fire or explosion risk.
- Fire may produce irritating, corrosive or toxic decomposition products.
- Runoff or wet absorbents can spread the reaction and create additional ignition hazards.
- Exact behavior depends on the product; verify SDS and shipping papers before tactical entry.
Chemical Identity & Physical Properties
Typically a white to yellow crystalline or powdered solid. Odor varies depending on specific substance. May emit irritating or toxic fumes when exposed to moisture The exact color, particle size and reactivity vary by the material shipped under this n.o.s. entry.
| Also known as | Water-reactive oxidizing solidOxidizing solid, water-reactiveDangerous when wet oxidizer |
| Appearance | Typically a white to yellow crystalline or powdered solid. Odor varies depending on specific substance. May emit irritating or toxic fumes when exposed to moisture. |
| Flash Point | Not applicable (solid, but ignites on contact with water) |
| Boiling Point | Not applicable (decomposes or reacts before boiling) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts violently with water producing flammable gases and heat; may ignite spontaneously. DO NOT USE WATER. |
Fireground Response Guidance — UN 3133
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical-protective clothing suitable for a water-reactive release. Level A may be needed if toxic gas, unknown identity or heavy vapor exposure is suspected.
Isolation & Evacuation
First Actions for a UN 3133 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 3133 — Water-reactive solid, oxidizing, 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.