☣️ UN 3402 • CLASS 4
UN 3402 — Alkaline earth metal amalgam, solid
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 3402 Quick Details
UN 3402
Product name: Alkaline earth metal amalgam, solid
DOT Class: 4
Placard type: Dangerous When Wet
ERG Guide: 138 (check current ERG)
Initial isolation: ERG 138: initial isolation 50m in all directions; if fire or large spill, isolate 800m in all directions and consider evacuation
Common Hazards of UN 3402
- 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 | Alkaline earth metal amalgamMercury-alkaline earth metal alloyCalcium amalgam solidBarium amalgam solidStrontium amalgam solid |
| Appearance | Silvery-gray to dark metallic solid or semi-solid alloy containing mercury and alkaline earth metals (calcium, barium, or strontium). May have a metallic sheen and can be brittle or pasty depending on composition. |
| Flash Point | Not applicable (water-reactive solid) |
| Boiling Point | Not applicable (decomposes upon heating or water contact) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts vigorously with water producing flammable hydrogen gas and heat; may ignite spontaneously in moist air or upon water contact |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3402
Extinguishing Media
Dry chemical, dry sand, soda ash, or dry graphite powder; never use water, foam, or CO2
PPE Requirements
⚠️ Level B minimum with full-face SCBA; chemical-resistant gloves and suit required; avoid moisture exposure during handling
Isolation & Evacuation
ERG 138: initial isolation 50m in all directions; if fire or large spill, isolate 800m in all directions and consider evacuation
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 138).
First Actions for a UN 3402 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 3402 — Alkaline earth metal amalgam, solidHAZMAT RADIO NOTE — UN 3402
Product: Alkaline earth metal amalgam, solid
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with full-face SCBA; chemical-resistant gloves and suit required; avoid moisture exposure during handling
ISOLATION: ERG 138: initial isolation 50m in all directions; if fire or large spill, isolate 800m in all directions 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 3402 — Alkaline earth metal amalgam, solid
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Silvery-gray to dark metallic solid or semi-solid alloy containing mercury and alkaline earth metals (calcium, barium, or strontium). May have a metallic sheen and can be brittle or pasty depending on composition.
Water Reactivity: Reacts vigorously with water producing flammable hydrogen gas and heat; may ignite spontaneously in moist air or upon water contact
Extinguishing: Dry chemical, dry sand, soda ash, or dry graphite powder; never use water, foam, or CO2
PPE: Level B minimum with full-face SCBA; chemical-resistant gloves and suit required; avoid moisture exposure during handling
Isolation: ERG 138: initial isolation 50m in all directions; if fire or large spill, isolate 800m in all directions and consider evacuation
— 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/3402 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3402 Alkaline earth metal amalgam, solid Cls4 ERG138 | allfirefighter.com/hazmat/un/3402SMS / 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/3402
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Frequently Asked Questions about UN 3402
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 full-face SCBA; chemical-resistant gloves and suit required; avoid moisture exposure during handling
Water reactivity: Reacts vigorously with water producing flammable hydrogen gas and heat; may ignite spontaneously in moist air or upon water contact. Recommended extinguishing: Dry chemical, dry sand, soda ash, or dry graphite powder; never use water, foam, or CO2.
ERG Guide 138 recommendation: ERG 138: initial isolation 50m in all directions; if fire or large spill, isolate 800m in all directions and consider evacuation
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.