☣️ UN 1298 • CLASS 3
UN 1298 — Trimethylchlorosilane
Placard: Flammable. ERG Guide 155. 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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UN 1298 Quick Details
UN 1298
Product name: Trimethylchlorosilane
DOT Class: 3
Placard type: Flammable
ERG Guide: 155 (check current ERG)
Initial isolation: ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind (day) or 800m (night). Fire: evacuate 800m radius.
Common Hazards of UN 1298
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
- Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
- Vapors may travel to source of ignition and flash back.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
- Corrosives in contact with metals may evolve flammable hydrogen gas.
- Containers may explode when heated or if contaminated with water.
Chemical Identity & Physical Properties
| Also known as | ChlorotrimethylsilaneTrimethylsilyl chlorideSilane, chlorotrimethyl-TMCSMonochlorotrimethylsilane |
| CAS Number | 75-77-4 |
| Appearance | Colorless to pale yellow liquid with a sharp, pungent, hydrochloric acid-like odor. Fuming liquid at room temperature when exposed to moist air. |
| Flash Point | -28C (-18F) |
| Boiling Point | 57C (135F) |
| Vapor Density | 3.8 (heavier than air) |
| Water Reactivity | Reacts violently with water producing hydrochloric acid fumes and hydrogen gas. Never use water directly on material. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1298
Extinguishing Media
Dry chemical, CO2, dry sand. DO NOT USE WATER OR FOAM. Water causes violent reaction.
PPE Requirements
⚠️ Level B minimum required. Full chemical protective suit with SCBA. Butyl rubber or Viton gloves recommended. Neoprene provides poor protection.
Isolation & Evacuation
ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind (day) or 800m (night). Fire: evacuate 800m radius.
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 155).
First Actions for a UN 1298 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
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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📋 Copy & Share Field Card
UN 1298 — TrimethylchlorosilaneHAZMAT RADIO NOTE — UN 1298
Product: Trimethylchlorosilane
Class 3 / Flammable / ERG 155
PPE: Level B minimum required. Full chemical protective suit with SCBA. Butyl rubber or Viton gloves recommended. Neoprene provides poor protection.
ISOLATION: ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind (day) or 800m (night). Fire: evacuate 800m radius.
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 1298 — Trimethylchlorosilane
Class: 3 | Placard: Flammable | ERG Guide: 155
Appearance: Colorless to pale yellow liquid with a sharp, pungent, hydrochloric acid-like odor. Fuming liquid at room temperature when exposed to moist air.
Water Reactivity: Reacts violently with water producing hydrochloric acid fumes and hydrogen gas. Never use water directly on material.
Extinguishing: Dry chemical, CO2, dry sand. DO NOT USE WATER OR FOAM. Water causes violent reaction.
PPE: Level B minimum required. Full chemical protective suit with SCBA. Butyl rubber or Viton gloves recommended. Neoprene provides poor protection.
Isolation: ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind (day) or 800m (night). Fire: evacuate 800m radius.
— Key Hazards —
• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
• Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
• Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
— 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/1298 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1298 Trimethylchlorosilane Cls3 ERG155 | ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind | allfirefighter.com/hazmat/un/1298SMS / 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/1298
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Frequently Asked Questions about UN 1298
HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards. Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas Vapors may travel to source of ignition and flash back. Those substances designated with a (P) may polymerize explosively when heated or involved in a fire. Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff. Corrosives in contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.
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 required. Full chemical protective suit with SCBA. Butyl rubber or Viton gloves recommended. Neoprene provides poor protection.
Water reactivity: Reacts violently with water producing hydrochloric acid fumes and hydrogen gas. Never use water directly on material.. Recommended extinguishing: Dry chemical, CO2, dry sand. DO NOT USE WATER OR FOAM. Water causes violent reaction..
ERG Guide 155 recommendation: ERG 155: Initial isolation 50m in all directions. Spill: evacuate 300m downwind (day) or 800m (night). Fire: evacuate 800m radius.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 155 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.