UN 3391 — Organometallic substance, solid, pyrophoric
Placard: Spontaneously Combustible. ERG Guide 135. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3391 is Organometallic substance, solid, pyrophoric, a broad organometallic entry assigned to ERG Guide 135. The main concern is pyrophoric air/moisture ignition; exact compound/SDS verification is critical.
Hazard overview: PYROPHORIC organometallic solid; may ignite spontaneously on exposure to air. Moist air or trace moisture can increase heat generation, burning and flammable gas release. May burn rapidly and re-ignite after apparent extinguishment.
Response guidance: For UN 3391, 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 135.
Firefighter training notes: Training for UN 3391 should emphasize pyrophoric/water-reactive behavior, dry-media tactics, re-ignition checks, moisture exclusion, SCBA use and runoff/debris control. Use ERG 135, SDS and local SOP.
Regulatory context: Organometallic substance, solid, pyrophoric 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: Organometallic substance, solid, pyrophoric 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 3391 Quick Details
Common Hazards of UN 3391
- PYROPHORIC organometallic solid; may ignite spontaneously on exposure to air.
- Moist air or trace moisture can increase heat generation, burning and flammable gas release.
- May burn rapidly and re-ignite after apparent extinguishment.
- Some compounds may decompose violently when heated or contaminated.
- Water, foam, CO2 or halogenated agents may worsen reaction or spread burning material.
- Fire may produce toxic metal oxide fumes, carbon monoxide and irritating organic smoke.
- Exact metal, ligand, solvent/wetting condition and package condition must be verified from SDS.
Chemical Identity & Physical Properties
Solid material of varying color depending on specific compound. May appear as powder, granules, or crystalline solid. Ignites spontaneously when exposed to air at room temperature.
| Also known as | Pyrophoric organometallic solidOrganometallic compound solid pyrophoricMetal-organic pyrophoric solid |
| Appearance | Solid material of varying color depending on specific compound. May appear as powder, granules, or crystalline solid. Ignites spontaneously when exposed to air at room temperature. |
| Flash Point | Not applicable (ignites spontaneously in air) |
| Boiling Point | Varies by specific compound |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts with moisture, may ignite or produce flammable gases. Keep completely dry. |
Fireground Response Guidance — UN 3391
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 3391 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 135, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 3391 — Organometallic substance, solid, pyrophoUse 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.