UN 2606 — Methyl orthosilicate
Placard: Toxic. ERG Guide 155. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2606 is Methyl orthosilicate, a toxic flammable alkoxysilane assigned to ERG Guide 155. Water can form methanol and silicic acid.
Hazard overview: TOXIC and FLAMMABLE alkoxysilane liquid; vapors may ignite and form explosive mixtures with air. Hydrolyzes with water or moisture to form methanol and silicic acid; reaction may generate heat. Vapors are heavier than air and may travel to ignition sources and flash back.
Response guidance: For UN 2606, isolate the area, eliminate ignition sources where relevant and use SCBA with chemical protection. Control water contact, contain toxic/corrosive runoff and choose agents using SDS and ERG 155.
Firefighter training notes: Training for UN 2606 should emphasize water/moisture reaction, toxic/corrosive vapor control, SCBA use, foam/dry-agent choice, decontamination and runoff containment. Use ERG 155, SDS and local SOP.
Regulatory context: Methyl orthosilicate 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: Methyl orthosilicate should be stored in tightly closed compatible containers with moisture control, ventilation, secondary containment and separation from heat, ignition sources, oxidizers and incompatible materials.
UN 2606 Quick Details
Common Hazards of UN 2606
- TOXIC and FLAMMABLE alkoxysilane liquid; vapors may ignite and form explosive mixtures with air.
- Hydrolyzes with water or moisture to form methanol and silicic acid; reaction may generate heat.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Methanol formation can add toxic and flammable vapor concerns.
- Liquid or vapor may irritate eyes, skin and respiratory tract.
- Runoff may carry toxic alcohol/silicate contamination.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Colorless liquid with a characteristic alcohol-like or ether-like odor. Liquid at room temperature.
| Also known as | Tetramethyl orthosilicateTetramethoxysilaneMethyl silicateSilicon tetramethoxideTetramethyl silicate |
| CAS Number | 681-84-5 |
| Appearance | Colorless liquid with a characteristic alcohol-like or ether-like odor. Liquid at room temperature. |
| Flash Point | -12C (10F) |
| Boiling Point | 121C (250F) |
| Vapor Density | 5.2 (heavier than air) |
| Water Reactivity | Reacts slowly with water, producing methanol and silicic acid. Reaction accelerates with heating. |
Fireground Response Guidance — UN 2606
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical-resistant protective clothing. Level A may be needed for heavy vapor, fuming, splash risk or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 2606 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, gas, mist, smoke or fumes and avoid skin or eye contact.
- Keep water or moisture contact controlled when it may increase reaction, fuming or gas generation.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 155, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2606 — Methyl orthosilicateUse 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.