UN 2189 — Dichlorosilane
Placard: Toxic Gas. ERG Guide 119. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2189 is Dichlorosilane, a toxic corrosive flammable gas assigned to ERG Guide 119. It reacts violently with moisture to release hydrogen chloride fumes.
Hazard overview: TOXIC, CORROSIVE and FLAMMABLE compressed gas; may ignite easily and form explosive mixtures with air. Reacts violently with water or moist air, releasing hydrogen chloride and heat. Gas/vapor may be heavier than air in cold or concentrated releases and may collect in low areas.
Response guidance: For a UN 2189 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 119. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2189 should emphasize flammable toxic gas behavior, water-reactive HCl fuming, source control, cylinder cooling, ignition control and Level A entry decisions. Use ERG 119, SDS and local SOP.
Regulatory context: Dichlorosilane is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting, waste handling and environmental requirements vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Dichlorosilane containers should be secured in a cool, ventilated gas storage area away from heat, physical damage and incompatible materials. Toxic, corrosive, oxidizing or refrigerated gases require leak detection/ventilation and emergency planning as specified by SDS and local code.
UN 2189 Quick Details
Common Hazards of UN 2189
- TOXIC, CORROSIVE and FLAMMABLE compressed gas; may ignite easily and form explosive mixtures with air.
- Reacts violently with water or moist air, releasing hydrogen chloride and heat.
- Gas/vapor may be heavier than air in cold or concentrated releases and may collect in low areas.
- Contact may cause chemical burns and frostbite from liquefied gas.
- Cylinders exposed to fire may vent, rupture or rocket.
- Fire may produce hydrogen chloride and silicon oxide/chloride fumes.
- Do not apply water directly to a release unless specialist guidance confirms compatibility.
Chemical Identity & Physical Properties
Colorless gas with a pungent, acrid odor. Liquefied under pressure. Extremely reactive and pyrophoric (ignites spontaneously in air).
| Also known as | DichlorosilaneSilicon dichlorideDCSSilylene dichlorideChlorosilane (SiH2Cl2) |
| CAS Number | 4109-96-0 |
| Appearance | Colorless gas with a pungent, acrid odor. Liquefied under pressure. Extremely reactive and pyrophoric (ignites spontaneously in air). |
| Flash Point | Not applicable (pyrophoric gas - ignites spontaneously in air) |
| Boiling Point | 8.3°C (47°F) |
| Vapor Density | 3.5 (heavier than air) |
| Water Reactivity | Reacts violently with water producing corrosive hydrochloric acid, hydrogen gas, and heat. Do not use water. |
Fireground Response Guidance — UN 2189
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and fully encapsulating chemical protective clothing for close entry or unknown concentrations. Level A may be needed; protect against frostbite where liquefied or refrigerated gas contact is possible.
Isolation & Evacuation
First Actions for a UN 2189 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, gas, dust, mist, smoke or fumes and avoid skin or eye contact.
- Eliminate ignition sources if safe and keep vapors and runoff out of drains, sewers, basements and low areas.
- Keep water and moisture away from the release unless specialist guidance confirms a compatible control use.
- Do not touch damaged containers or spilled/released 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 release area and expand the perimeter for fire involvement, vapor spread, gas accumulation, cylinder heating or unknown product identity.
- Use ERG Guide 119, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2189 — DichlorosilaneUse 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.