UN 1781 — Hexadecyltrichlorosilane
Placard: Corrosive. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1781 is Hexadecyltrichlorosilane, a corrosive chlorosilane assigned to ERG Guide 156. It reacts violently with moisture, releasing heat and hydrogen chloride fumes.
Hazard overview: UN 1781 presents water-reactive, corrosive fume, heavy vapor and combustible/flammable liquid hazards. Do not apply water directly to the material; use dry compatible agents and control ignition sources where relevant.
Response guidance: For a UN 1781 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 156. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1781 should emphasize water-reactive chlorosilane behavior, HCl fuming, heavy vapor movement, ignition control where relevant, dry-agent selection and runoff containment. Use ERG 156, SDS and local SOP.
Regulatory context: Hexadecyltrichlorosilane is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by concentration, formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Hexadecyltrichlorosilane should be stored in tightly closed compatible containers in a cool, dry, well-ventilated area away from water, moisture, bases, oxidizers/reducing agents where incompatible, heat and unauthorized access. Protect containers from corrosion, leakage and contamination.
UN 1781 Quick Details
Common Hazards of UN 1781
- COMBUSTIBLE and CORROSIVE chlorosilane; vapors may ignite or form explosive mixtures when heated.
- Reacts violently with water or moist air, releasing heat and corrosive hydrogen chloride fumes.
- Vapors are heavier than air and may collect in low or confined areas.
- Liquid and fumes can burn eyes, skin and respiratory tissue.
- Corrosive runoff may damage equipment and contaminate drains.
- Containers may rupture or explode when heated or contaminated with water.
- Do not apply water or foam directly to the material.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, acrid, hydrochloric acid-like odor. Corrosive organosilicon compound that fumes in moist air.
| Also known as | Hexadecyltrichlorosilanen-HexadecyltrichlorosilaneCetyl trichlorosilaneTrichlorohexadecylsilane |
| CAS Number | 5894-60-0 |
| Appearance | Colorless to pale yellow liquid with a pungent, acrid, hydrochloric acid-like odor. Corrosive organosilicon compound that fumes in moist air. |
| Flash Point | 93C (200F) — combustible liquid |
| Boiling Point | Approximately 333C (631F) at 760 mmHg |
| Vapor Density | Approximately 10 (heavier than air, relative to air=1) |
| Water Reactivity | Reacts violently with water, releasing heat and toxic/corrosive hydrogen chloride gas (HCl). Do not use water directly on material. |
Fireground Response Guidance — UN 1781
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fume, fire or confined-space exposure. Chemical-resistant gloves, boots, eye/face protection and protective clothing should be selected from SDS; Level A may be needed for close entry or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 1781 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, fumes, dust, mist or spray and avoid skin or eye contact.
- Eliminate ignition sources if safe and keep vapors or runoff out of drains, sewers and low areas.
- Keep water and moisture away from released product unless incident command confirms a compatible cooling or control use.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if vapor, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 156, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1781 — HexadecyltrichlorosilaneUse 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.