☣️ UN 3397 • CLASS 4
UN 3397 — Organometallic substance, solid, water-reactive, selfheating
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 3397 Quick Details
UN 3397
Product name: Organometallic substance, solid, water-reactive, selfheating
DOT Class: 4
Placard type: Dangerous When Wet
ERG Guide: 138 (check current ERG)
Initial isolation: ERG 138: isolate 25m all directions initially; if fire or large spill isolate 800m and evacuate 1600m downwind
Common Hazards of UN 3397
- 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 | Organometallic compound, solid, water-reactivePyrophoric organometallic solidWater-reactive metal-organic compound |
| Appearance | Solid material varying in color from gray to dark metallic, typically odorless or with slight metallic odor. Spontaneously combustible when exposed to air or moisture. |
| Flash Point | Not applicable (pyrophoric material) |
| Boiling Point | Not applicable (decomposes) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts violently with water producing flammable gases and heat; may ignite spontaneously |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3397
Extinguishing Media
Dry sand, dry chemical, soda ash; NO WATER, NO FOAM
PPE Requirements
⚠️ Level A minimum; SCBA required; chemical-resistant suit; avoid moisture contact
Isolation & Evacuation
ERG 138: isolate 25m all directions initially; if fire or large spill isolate 800m and evacuate 1600m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 138).
First Actions for a UN 3397 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 3397 — Organometallic substance, solid, water-rHAZMAT RADIO NOTE — UN 3397
Product: Organometallic substance, solid, water-reactive, selfheating
Class 4 / Dangerous When Wet / ERG 138
PPE: Level A minimum; SCBA required; chemical-resistant suit; avoid moisture contact
ISOLATION: ERG 138: isolate 25m all directions initially; if fire or large spill isolate 800m and evacuate 1600m 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 3397 — Organometallic substance, solid, water-reactive, selfheating
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Solid material varying in color from gray to dark metallic, typically odorless or with slight metallic odor. Spontaneously combustible when exposed to air or moisture.
Water Reactivity: Reacts violently with water producing flammable gases and heat; may ignite spontaneously
Extinguishing: Dry sand, dry chemical, soda ash; NO WATER, NO FOAM
PPE: Level A minimum; SCBA required; chemical-resistant suit; avoid moisture contact
Isolation: ERG 138: isolate 25m all directions initially; if fire or large spill isolate 800m and evacuate 1600m 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/3397 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3397 Organometallic substance, solid, water-reactive, selfheating Cls4 ERG138 | allfirefighter.com/hazmat/un/3397SMS / 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/3397
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Frequently Asked Questions about UN 3397
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 A minimum; SCBA required; chemical-resistant suit; avoid moisture contact
Water reactivity: Reacts violently with water producing flammable gases and heat; may ignite spontaneously. Recommended extinguishing: Dry sand, dry chemical, soda ash; NO WATER, NO FOAM.
ERG Guide 138 recommendation: ERG 138: isolate 25m all directions initially; if fire or large spill isolate 800m and evacuate 1600m 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.