UN 3401 — Alkali metal amalgam, solid
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3401 is Alkali metal amalgam, solid, a dangerous-when-wet metal amalgam assigned to ERG Guide 138. Hydrogen generation and mercury contamination are key concerns.
Hazard overview: DANGEROUS WHEN WET metal amalgam; water or moisture can release flammable hydrogen and heat. Contains mercury with alkali or alkaline-earth metal; toxic mercury contamination is a secondary concern. May ignite on contact with moisture, especially if finely divided or damaged.
Response guidance: For UN 3401, 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 3401 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: Alkali metal amalgam, 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: Alkali metal amalgam, 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 3401 Quick Details
Common Hazards of UN 3401
- DANGEROUS WHEN WET metal amalgam; water or moisture can release flammable hydrogen and heat.
- Contains mercury with alkali or alkaline-earth metal; toxic mercury contamination is a secondary concern.
- May ignite on contact with moisture, especially if finely divided or damaged.
- Water, foam, CO2 and halogenated agents can worsen reaction or spread burning material.
- Fire may produce mercury vapor, metal oxide fumes and caustic residue.
- Runoff may carry mercury and alkaline contamination.
- Exact alloy composition and physical state must be verified from SDS.
Chemical Identity & Physical Properties
Silvery-white to gray metallic solid or semi-solid material. Odorless. Amalgam is an alloy of mercury with sodium, potassium, lithium, or other alkali metals in solid form at room temperature.
| Also known as | Sodium amalgamPotassium amalgamLithium amalgamMercury-alkali metal alloy |
| Appearance | Silvery-white to gray metallic solid or semi-solid material. Odorless. Amalgam is an alloy of mercury with sodium, potassium, lithium, or other alkali metals in solid form at room temperature. |
| Flash Point | Not applicable (water-reactive solid, produces flammable hydrogen gas) |
| Boiling Point | Not applicable (decomposes on heating) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts vigorously to violently with water, producing flammable hydrogen gas and heat. May ignite spontaneously on contact with moist air or water. Do not use water. |
Fireground Response Guidance — UN 3401
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 3401 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 3401 — Alkali metal amalgam, 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.