☣️ UN 1250 • CLASS 3
Methyltrichlorosilane
Placard: Flammable. 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 1250
Class: 3
Placard type: Flammable
ERG: Guide 155 (check current ERG)
Isolation: ERG 155: Isolate spill 50m all directions. Evacuate 800m downwind if tank/rail car involved in fire.
Chemical & Response Details
| Also known as | TrichloromethylsilaneMethyl trichlorosilaneSilane, trichloromethyl-Methylsilicon trichloride |
| CAS Number | 75-79-6 |
| Appearance | Colorless to pale yellow fuming liquid with a pungent, acrid odor. Fumes in moist air due to reaction with atmospheric moisture. |
| Flash Point | -9C (15F) |
| Boiling Point | 66C (151F) |
| Vapor Density | 5.2 (heavier than air) |
| Water Reactivity | Reacts violently with water producing heat, hydrogen chloride fumes, and flammable hydrogen gas. Keep away from water. |
| Extinguishing | Dry chemical, CO2, dry sand. Do not use water or foam; may react violently. |
| PPE | ⚠️ Level A or B minimum; SCBA required; full chemical-resistant suit due to corrosive fumes and water reactivity. |
| Isolation | ERG 155: Isolate spill 50m all directions. Evacuate 800m downwind if tank/rail car involved in fire. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
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
- 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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UN 1250 — Methyltrichlorosilane HAZMAT RADIO NOTE — UN 1250
Product: Methyltrichlorosilane
Class 3 / Flammable / ERG 155
PPE: Level A or B minimum; SCBA required; full chemical-resistant suit due to corrosive fumes and water reactivity.
ISOLATION: ERG 155: Isolate spill 50m all directions. Evacuate 800m downwind if tank/rail car involved in fire.
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 1250 — Methyltrichlorosilane
Class: 3 | Placard: Flammable | ERG Guide: 155
Appearance: Colorless to pale yellow fuming liquid with a pungent, acrid odor. Fumes in moist air due to reaction with atmospheric moisture.
Water Reactivity: Reacts violently with water producing heat, hydrogen chloride fumes, and flammable hydrogen gas. Keep away from water.
Extinguishing: Dry chemical, CO2, dry sand. Do not use water or foam; may react violently.
PPE: Level A or B minimum; SCBA required; full chemical-resistant suit due to corrosive fumes and water reactivity.
Isolation: ERG 155: Isolate spill 50m all directions. Evacuate 800m downwind if tank/rail car involved in fire.
— 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/1250 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1250 Methyltrichlorosilane Cls3 ERG155 | ERG 155: Isolate spill 50m all directions. Evacuate 800m downwind if tank/rail c | allfirefighter.com/hazmat/un/1250SMS / 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/1250
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FAQ
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 A or B minimum; SCBA required; full chemical-resistant suit due to corrosive fumes and water reactivity.
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.