☣️ UN 1398 • CLASS 4
Aluminum silicon powder, uncoated
Placard: Dangerous When Wet. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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 1398
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: Isolate spill area immediate 25m in all directions. For large spills isolate 50m. If fire, evacuate 800m radius. Keep material dry at all times.
Chemical & Response Details
| Also known as | Aluminum-silicon alloy powderAl-Si powderFerrosilicon aluminum powderUncoated aluminum silicon powder |
| Appearance | Gray to dark gray metallic powder. Odorless. Solid at room temperature with a fine to coarse granular texture. |
| Flash Point | Not applicable (pyrophoric/water-reactive solid) |
| Boiling Point | Not applicable (metal alloy powder) |
| Vapor Density | Not applicable (solid powder) |
| Water Reactivity | Reacts with water to produce flammable hydrogen gas. May ignite spontaneously on contact with water or moist air. Reaction can be vigorous to violent depending on moisture content. |
| Extinguishing | Dry sand, dry chemical, soda ash, or dry graphite. DO NOT use water, foam, CO2, or halogenated agents. |
| PPE | ⚠️ Level B minimum for spills. SCBA and full protective clothing required for fires. Avoid all moisture contact. Use non-sparking tools. |
| Isolation | ERG 138: Isolate spill area immediate 25m in all directions. For large spills isolate 50m. If fire, evacuate 800m radius. Keep material dry at all times. |
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 1398 — Aluminum silicon powder, uncoated HAZMAT RADIO NOTE — UN 1398
Product: Aluminum silicon powder, uncoated
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum for spills. SCBA and full protective clothing required for fires. Avoid all moisture contact. Use non-sparking tools.
ISOLATION: ERG 138: Isolate spill area immediate 25m in all directions. For large spills isolate 50m. If fire, evacuate 800m radius. Keep material dry at all times.
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 1398 — Aluminum silicon powder, uncoated
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Gray to dark gray metallic powder. Odorless. Solid at room temperature with a fine to coarse granular texture.
Water Reactivity: Reacts with water to produce flammable hydrogen gas. May ignite spontaneously on contact with water or moist air. Reaction can be vigorous to violent depending on moisture content.
Extinguishing: Dry sand, dry chemical, soda ash, or dry graphite. DO NOT use water, foam, CO2, or halogenated agents.
PPE: Level B minimum for spills. SCBA and full protective clothing required for fires. Avoid all moisture contact. Use non-sparking tools.
Isolation: ERG 138: Isolate spill area immediate 25m in all directions. For large spills isolate 50m. If fire, evacuate 800m radius. Keep material dry at all times.
— 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/1398 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1398 Aluminum silicon powder, uncoated Cls4 ERG138 | allfirefighter.com/hazmat/un/1398SMS / 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/1398
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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 for spills. SCBA and full protective clothing required for fires. Avoid all moisture contact. Use non-sparking tools.
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.