☣️ UN 1398 • CLASS 4
UN 1398 — Aluminum silicon powder, uncoated
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.
Aluminum silicon powder, uncoated is a highly reactive substance that can ignite spontaneously when wet or in contact with moist air. It is essential to handle this material with caution.
Hazard overview: Aluminum silicon powder, uncoated can produce flammable gases on contact with water, and may ignite on contact with water or moist air. This can lead to violent reactions and fires.
Response guidance: In the event of a spill, isolate the area immediately and keep it dry. For fires, use dry agents such as sand, dry chemical, or soda ash, and avoid using water or foam.
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UN 1398 Quick Details
UN 1398
Product name: Aluminum silicon powder, uncoated
DOT Class: 4
Placard type: Dangerous When Wet
ERG Guide: 138 (check current ERG)
Initial 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.
Common Hazards of UN 1398
- 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
Aluminum silicon powder, uncoated is a gray to dark gray metallic powder with an odorless odor.
| 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. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1398
Extinguishing Media
Dry sand, dry chemical, soda ash, or dry graphite. DO NOT use water, foam, CO2, or halogenated agents.
PPE Requirements
⚠️ Level B minimum for spills. SCBA and full protective clothing required for fires. Avoid all moisture contact. Use non-sparking tools.
Wear Level B minimum personal protective equipment (PPE) with a self-contained breathing apparatus (SCBA) and full protective clothing to handle aluminum silicon powder, uncoated.
Isolation & Evacuation
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.
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 138).
First Actions for a UN 1398 Incident
- 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 1398 — Aluminum silicon powder, uncoatedHAZMAT 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 —
• 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
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.
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.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/aluminum-silicon-powder-uncoated-un-1398
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Frequently Asked Questions about UN 1398
Yes, aluminum silicon powder, uncoated can ignite spontaneously when wet or in contact with moist air.
No, do not use water or foam to extinguish a fire involving aluminum silicon powder, uncoated.
Isolate the spill area immediately and keep it dry.
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.