☣️ UN 1346 • CLASS 4
Silicon powder, amorphous
Placard: Flammable Solid. 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 1346
Class: 4
Placard type: Flammable Solid
ERG: Guide 170 (check current ERG)
Isolation: ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate downwind
Chemical & Response Details
| Also known as | Amorphous siliconSilicon dustSilicium powderNon-crystalline silicon |
| CAS Number | 7440-21-3 |
| Appearance | Dark gray to black fine powder with no odor. Exists as a solid at room temperature in amorphous (non-crystalline) form. |
| Flash Point | Not applicable (combustible solid, ignites at approximately 1414C/2577F) |
| Boiling Point | 2355C (4271F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | May react with water, especially when hot or finely divided, releasing hydrogen gas |
| Extinguishing | Dry chemical, dry sand, soda ash; do not use water or foam |
| PPE | ⚠️ Level C minimum; SCBA if burning or dust cloud present; protective gloves and eye protection required |
| Isolation | ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate downwind |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- May react violently or explosively on contact with water.
- Some are transported in flammable liquids.
- May be ignited by friction, heat, sparks or flames.
- Some of these materials will burn with intense heat.
- Dusts or fumes may form explosive mixtures in air.
- Containers may explode when heated.
- May re-ignite after fire is extinguished.
- Oxides from metallic fires are a severe health hazard.
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
- Consider initial downwind evacuation for at least 50 meters (160 feet).
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UN 1346 — Silicon powder, amorphous HAZMAT RADIO NOTE — UN 1346
Product: Silicon powder, amorphous
Class 4 / Flammable Solid / ERG 170
PPE: Level C minimum; SCBA if burning or dust cloud present; protective gloves and eye protection required
ISOLATION: ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate 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 1346 — Silicon powder, amorphous
Class: 4 | Placard: Flammable Solid | ERG Guide: 170
Appearance: Dark gray to black fine powder with no odor. Exists as a solid at room temperature in amorphous (non-crystalline) form.
Water Reactivity: May react with water, especially when hot or finely divided, releasing hydrogen gas
Extinguishing: Dry chemical, dry sand, soda ash; do not use water or foam
PPE: Level C minimum; SCBA if burning or dust cloud present; protective gloves and eye protection required
Isolation: ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate downwind
— Key Hazards —
• May react violently or explosively on contact with water.
• Some are transported in flammable liquids.
• May be ignited by friction, heat, sparks or flames.
— 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/1346 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1346 Silicon powder, amorphous Cls4 ERG170 | allfirefighter.com/hazmat/un/1346SMS / 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/1346
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FAQ
May react violently or explosively on contact with water. Some are transported in flammable liquids. May be ignited by friction, heat, sparks or flames. Some of these materials will burn with intense heat. Dusts or fumes may form explosive mixtures in air. Containers may explode when heated. May re-ignite after fire is extinguished. Oxides from metallic fires are a severe health hazard.
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 C minimum; SCBA if burning or dust cloud present; protective gloves and eye protection required
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 170 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.