UN 2749 — Tetramethylsilane
Placard: Flammable. ERG Guide 130. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2749 is Tetramethylsilane, a highly flammable volatile organosilicon liquid assigned to ERG Guide 130. Vapor flashback and sewer explosion are priorities.
Hazard overview: HIGHLY FLAMMABLE volatile organosilicon liquid; vapors may ignite easily and form explosive mixtures with air. Vapors are heavier than air and may travel to ignition sources and flash back. Vapor explosion hazard exists in drains, basements, sewers and confined areas.
Response guidance: For UN 2749, isolate the area, eliminate ignition sources and use SCBA. Keep vapors out of drains, cool containers from protection and contain toxic runoff using SDS and ERG 130.
Firefighter training notes: Training for UN 2749 should emphasize vapor travel, toxic exposure routes, SCBA use, fire behavior, decontamination, runoff containment and SDS verification. Use ERG 130, SDS and local SOP.
Regulatory context: Tetramethylsilane is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Tetramethylsilane should be stored in approved flammable-liquid containers with ventilation, bonding/grounding where required, spill containment and separation from heat, ignition sources and oxidizers.
UN 2749 Quick Details
Common Hazards of UN 2749
- HIGHLY FLAMMABLE volatile organosilicon liquid; vapors may ignite easily and form explosive mixtures with air.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Vapor explosion hazard exists in drains, basements, sewers and confined areas.
- Liquid is insoluble in water and may float, spreading fire or contamination.
- Runoff to sewers may create fire or explosion hazards.
- Fire may produce silicon oxides, carbon monoxide and irritating smoke.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Colorless liquid with a characteristic odor. Highly volatile at room temperature.
| Also known as | TMSTetramethyl silaneSilicon tetramethylSilane, tetramethyl- |
| CAS Number | 75-76-3 |
| Appearance | Colorless liquid with a characteristic odor. Highly volatile at room temperature. |
| Flash Point | -27C (-17F) |
| Boiling Point | 27C (81F) |
| Vapor Density | 3.0 (heavier than air) |
| Water Reactivity | No significant reaction; insoluble in water |
Fireground Response Guidance — UN 2749
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, dust, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing.
Isolation & Evacuation
First Actions for a UN 2749 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Eliminate ignition sources if this can be done safely.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Prevent contaminated liquid, dust, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 130, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2749 — TetramethylsilaneUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.