☣️ UN 1346 • CLASS 4
UN 1346 — Silicon powder, amorphous
Placard: Flammable Solid. ERG Guide 170. 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.
Silicon powder is a highly reactive solid that may react violently or explosively on contact with water.
Hazard overview: Silicon powder may react violently or explosively on contact with water and some forms are transported in flammable liquids.
Response guidance: In case of fire, use dry chemical, dry sand, or soda ash. Do not use water or foam, as it may react with the silicon powder.
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UN 1346 Quick Details
UN 1346
Product name: Silicon powder, amorphous
DOT Class: 4
Placard type: Flammable Solid
ERG Guide: 170 (check current ERG)
Initial isolation: ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate downwind
Common Hazards of UN 1346
- 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.
Chemical Identity & Physical Properties
Silicon powder is a dark gray to black fine powder with no odor.
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1346
Extinguishing Media
Dry chemical, dry sand, soda ash; do not use water or foam
PPE Requirements
⚠️ Level C minimum; SCBA if burning or dust cloud present; protective gloves and eye protection required
Level C minimum PPE is required for handling silicon powder, while SCBA is required if burning or dust cloud is present.
Isolation & Evacuation
ERG 170: isolate 25m in all directions initially; if fire or large spill, isolate 800m and evacuate downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 170).
First Actions for a UN 1346 Incident
- 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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📋 Copy & Share Field Card
UN 1346 — Silicon powder, amorphousHAZMAT 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 —
• 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).
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.
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.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/silicon-powder-amorphous-un-1346
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Frequently Asked Questions about UN 1346
Some forms of Silicon Powder are transported in flammable liquids.
No, do not use water on Silicon Powder, as it may react violently or explosively.
Level C minimum PPE is required, while SCBA is required if burning or dust cloud is present.
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.