☣️ UN 3208 • CLASS 4
Metallic substance, waterreactive, n.o.s.
Placard: Dangerous When Wet. 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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Quick details
UN 3208
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: isolate spill 25m all directions; if fire or leak, isolate 800m initially, evacuate 800m downwind
Chemical & Response Details
| Also known as | Water-reactive metalMetal powder water-reactiveReactive metallic substancePyrophoric metal compound |
| Appearance | Solid metallic powder, granules, or chunks; appearance varies widely by specific metal (gray, silvery, or dark); may be odorless or have metallic smell; typically shipped in sealed containers to prevent moisture contact. |
| Flash Point | Not applicable (ignites spontaneously on contact with water) |
| Boiling Point | Not applicable (varies by specific metal constituent) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts violently with water producing flammable hydrogen or other gases; may ignite spontaneously; DO NOT USE WATER |
| Extinguishing | Dry sand, dry chemical, soda ash, dry ground limestone; NO WATER or FOAM containing water |
| PPE | ⚠️ Level B minimum with SCBA; face shield and chemical-resistant gloves; avoid moisture exposure during handling |
| Isolation | ERG 138: isolate spill 25m all directions; if fire or leak, isolate 800m initially, evacuate 800m downwind |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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
First actions (field-minded)
- 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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UN 3208 — Metallic substance, waterreactive, n.o.s HAZMAT RADIO NOTE — UN 3208
Product: Metallic substance, waterreactive, n.o.s.
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with SCBA; face shield and chemical-resistant gloves; avoid moisture exposure during handling
ISOLATION: ERG 138: isolate spill 25m all directions; if fire or leak, isolate 800m initially, 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 3208 — Metallic substance, waterreactive, n.o.s.
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Solid metallic powder, granules, or chunks; appearance varies widely by specific metal (gray, silvery, or dark); may be odorless or have metallic smell; typically shipped in sealed containers to prevent moisture contact.
Water Reactivity: Reacts violently with water producing flammable hydrogen or other gases; may ignite spontaneously; DO NOT USE WATER
Extinguishing: Dry sand, dry chemical, soda ash, dry ground limestone; NO WATER or FOAM containing water
PPE: Level B minimum with SCBA; face shield and chemical-resistant gloves; avoid moisture exposure during handling
Isolation: ERG 138: isolate spill 25m all directions; if fire or leak, isolate 800m initially, 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/3208 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3208 Metallic substance, waterreactive, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/3208SMS / 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/3208
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FAQ
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 and chemical-resistant gloves; avoid moisture exposure during handling
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.