☣️ UN 3398 • CLASS 4
Organometallic substance, liquid, water-reactive
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 3398
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 135 (check current ERG)
Isolation: ERG 135: Initial isolation 50m all directions. Protect from water/moisture. For fire, isolate 800m and consider evacuation.
Chemical & Response Details
| Also known as | Organometallic compound liquidOrganometallic solutionWater-reactive organometallic liquidPyrophoric organometallic substance |
| Appearance | Varies widely depending on specific compound; typically colorless to pale yellow liquids with characteristic organic or metallic odors. Many are spontaneously flammable in air. |
| Flash Point | Not applicable (spontaneously combustible) |
| Boiling Point | Varies by specific compound |
| Vapor Density | Typically >1 (heavier than air) |
| Water Reactivity | Reacts violently with water, producing flammable gases and heat. May ignite spontaneously. DO NOT use water. |
| Extinguishing | Dry sand, dry chemical, soda ash, or dry clay for small fires. For large fires, withdraw and let burn. NO WATER OR FOAM. |
| PPE | ⚠️ Level B minimum required. Full-face SCBA, chemical-resistant suit. Self-contained breathing apparatus mandatory. Avoid all moisture contact. |
| Isolation | ERG 135: Initial isolation 50m all directions. Protect from water/moisture. For fire, isolate 800m and consider evacuation. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Flammable/combustible material.
- May ignite on contact with moist air or moisture.
- May burn rapidly with flare-burning effect.
- Some react vigorously or explosively on contact with water.
- Some may decompose explosively when heated or involved in a fire.
- May re-ignite after fire is extinguished.
- Runoff may create fire or explosion hazard.
- Containers may explode when heated.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Stay upwind, uphill and/or upstream.
- Keep unauthorized personnel away.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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UN 3398 — Organometallic substance, liquid, water- HAZMAT RADIO NOTE — UN 3398
Product: Organometallic substance, liquid, water-reactive
Class 4 / Dangerous When Wet / ERG 135
PPE: Level B minimum required. Full-face SCBA, chemical-resistant suit. Self-contained breathing apparatus mandatory. Avoid all moisture contact.
ISOLATION: ERG 135: Initial isolation 50m all directions. Protect from water/moisture. For fire, isolate 800m and consider evacuation.
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 3398 — Organometallic substance, liquid, water-reactive
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 135
Appearance: Varies widely depending on specific compound; typically colorless to pale yellow liquids with characteristic organic or metallic odors. Many are spontaneously flammable in air.
Water Reactivity: Reacts violently with water, producing flammable gases and heat. May ignite spontaneously. DO NOT use water.
Extinguishing: Dry sand, dry chemical, soda ash, or dry clay for small fires. For large fires, withdraw and let burn. NO WATER OR FOAM.
PPE: Level B minimum required. Full-face SCBA, chemical-resistant suit. Self-contained breathing apparatus mandatory. Avoid all moisture contact.
Isolation: ERG 135: Initial isolation 50m all directions. Protect from water/moisture. For fire, isolate 800m and consider evacuation.
— Key Hazards —
• Flammable/combustible material.
• May ignite on contact with moist air or moisture.
• May burn rapidly with flare-burning effect.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Stay upwind, uphill and/or upstream.
• Keep unauthorized personnel away.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/3398 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3398 Organometallic substance, liquid, water-reactive Cls4 ERG135 | allfirefighter.com/hazmat/un/3398SMS / 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/3398
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FAQ
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Stay upwind, uphill and/or upstream. Keep unauthorized personnel away.
Level B minimum required. Full-face SCBA, chemical-resistant suit. Self-contained breathing apparatus mandatory. Avoid all moisture contact.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 135 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.