UN 3404 — Potassium sodium alloys, solid
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3404 is Potassium sodium alloys, solid, a dangerous-when-wet potassium alloy assigned to ERG Guide 138. Water can cause violent hydrogen release and ignition.
Hazard overview: DANGEROUS WHEN WET potassium-containing metal alloy; water can react violently or explosively. Water or moist air may release flammable hydrogen gas, heat and ignition. Material may be solid, semi-solid or liquid depending on alloy composition and temperature.
Response guidance: For UN 3404, isolate the area, keep all water/moisture away and use SCBA from a protected position. Use compatible dry media only and watch for re-ignition under ERG 138.
Firefighter training notes: Training for UN 3404 should emphasize pyrophoric/water-reactive behavior, dry-media tactics, re-ignition checks, moisture exclusion, SCBA use and runoff/debris control. Use ERG 138, SDS and local SOP.
Regulatory context: Potassium sodium alloys, solid is regulated as a hazardous material for transport and emergency response. Storage, reporting, exposure, waste and incident-notification duties depend on quantity, concentration, formulation and jurisdiction; verify shipping papers, SDS and authority guidance.
Storage & handling: Potassium sodium alloys, solid should be stored dry in compatible sealed containers under inert gas or approved protective liquid where required, away from water, moisture, air, heat, ignition sources and oxidizers.
UN 3404 Quick Details
Common Hazards of UN 3404
- DANGEROUS WHEN WET potassium-containing metal alloy; water can react violently or explosively.
- Water or moist air may release flammable hydrogen gas, heat and ignition.
- Material may be solid, semi-solid or liquid depending on alloy composition and temperature.
- Water, foam, CO2 and halogenated agents are incompatible with burning or spilled material.
- May re-ignite after apparent extinguishment if reactive metal remains exposed.
- Fire may produce caustic potassium/sodium oxides and metal fumes.
- Exact alloy composition, storage oil/inerting and temperature must be verified.
Chemical Identity & Physical Properties
Silvery-white metallic solid or liquid at room temperature depending on composition. Typical eutectic alloy (22% Na, 78% K) is liquid above -12.6°C. Lustrous appearance when fresh, tarnishes rapidly in air.
| Also known as | NaK alloySodium-potassium alloyLiquid metal coolantNaK eutectic |
| CAS Number | 11135-81-2 |
| Appearance | Silvery-white metallic solid or liquid at room temperature depending on composition. Typical eutectic alloy (22% Na, 78% K) is liquid above -12.6°C. Lustrous appearance when fresh, tarnishes rapidly in air. |
| Flash Point | Not applicable (spontaneously ignites with water/moist air) |
| Boiling Point | 784°C (1443°F) for eutectic composition |
| Vapor Density | Not applicable (metal, negligible vapor pressure at ambient) |
| Water Reactivity | Reacts violently and explosively with water, producing flammable hydrogen gas and heat. May ignite spontaneously. Never use water for extinguishment or cleanup. |
Fireground Response Guidance — UN 3404
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA with fire/chemical protection and distance from reactive material. Level A or B may be needed for unknown compound, vapor, splash or residue contact.
Isolation & Evacuation
First Actions for a UN 3404 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Exclude water, moisture, foam and incompatible extinguishing media.
- Avoid disturbing residue because pyrophoric or water-reactive material may re-ignite.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Prevent contaminated liquid, dust, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 138, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 3404 — Potassium sodium alloys, solidUse 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.