☣️ UN 3209 • CLASS 4
UN 3209 — Metallic substance, waterreactive, self-heating, n.o.s.
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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UN 3209 Quick Details
UN 3209
Product name: Metallic substance, waterreactive, self-heating, n.o.s.
DOT Class: 4
Placard type: Dangerous When Wet
ERG Guide: 138 (check current ERG)
Initial isolation: ERG 138: isolate spill 25m all directions; if fire or large spill, isolate 800m and evacuate 800m downwind
Common Hazards of UN 3209
- Produce flammable gases on contact with water.
- May ignite on contact with water or moist air.
- Some react vigorously or explosively on contact with water.
- May be ignited by heat, sparks or flames.
- May re-ignite after fire is extinguished.
- Some are transported in highly flammable liquids.
- Runoff may create fire or explosion hazard.
- Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
Chemical Identity & Physical Properties
| Also known as | Water-reactive metalSelf-heating metallic materialPyrophoric metal substance |
| Appearance | Metallic solid or powder, appearance varies by specific metal. May be gray, silver, or dark colored. Odorless in dry state. |
| Flash Point | Not applicable (reacts with water to produce flammable gas) |
| Boiling Point | Not applicable (solid metal, varies by specific substance) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts with water producing flammable hydrogen or other gases; may ignite spontaneously on contact with moisture or humid air |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3209
Extinguishing Media
Dry sand, dry chemical, soda ash; DO NOT use water, foam, CO2, or halogenated agents
PPE Requirements
⚠️ Level B minimum with SCBA; face shield, chemical-resistant gloves; avoid moisture exposure during handling
Isolation & Evacuation
ERG 138: isolate spill 25m all directions; if fire or large spill, isolate 800m and evacuate 800m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 138).
First Actions for a UN 3209 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
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📋 Copy & Share Field Card
UN 3209 — Metallic substance, waterreactive, self-HAZMAT RADIO NOTE — UN 3209
Product: Metallic substance, waterreactive, self-heating, n.o.s.
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with SCBA; face shield, chemical-resistant gloves; avoid moisture exposure during handling
ISOLATION: ERG 138: isolate spill 25m all directions; if fire or large spill, isolate 800m and evacuate 800m downwind
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3209 — Metallic substance, waterreactive, self-heating, n.o.s.
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Metallic solid or powder, appearance varies by specific metal. May be gray, silver, or dark colored. Odorless in dry state.
Water Reactivity: Reacts with water producing flammable hydrogen or other gases; may ignite spontaneously on contact with moisture or humid air
Extinguishing: Dry sand, dry chemical, soda ash; DO NOT use water, foam, CO2, or halogenated agents
PPE: Level B minimum with SCBA; face shield, chemical-resistant gloves; avoid moisture exposure during handling
Isolation: ERG 138: isolate spill 25m all directions; if fire or large spill, isolate 800m and evacuate 800m downwind
— Key Hazards —
• Produce flammable gases on contact with water.
• May ignite on contact with water or moist air.
• Some react vigorously or explosively on contact with water.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/3209 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3209 Metallic substance, waterreactive, self-heating, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/3209SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/3209
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Frequently Asked Questions about UN 3209
Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard. Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum with SCBA; face shield, chemical-resistant gloves; avoid moisture exposure during handling
Water reactivity: Reacts with water producing flammable hydrogen or other gases; may ignite spontaneously on contact with moisture or humid air. Recommended extinguishing: Dry sand, dry chemical, soda ash; DO NOT use water, foam, CO2, or halogenated agents.
ERG Guide 138 recommendation: ERG 138: isolate spill 25m all directions; if fire or large spill, isolate 800m and evacuate 800m downwind
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 138 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles.
This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.