UN 2328 — Trimethylhexamethylene diisocyanate
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2328 is Trimethylhexamethylene diisocyanate, a toxic diisocyanate liquid assigned to ERG Guide 156. Inhalation can cause respiratory sensitization and water reaction can build pressure.
Hazard overview: TOXIC isocyanate liquid; inhalation of vapor or aerosol may cause severe respiratory sensitization and injury. Combustible material: may burn but does not ignite readily. Reacts with water to release carbon dioxide, heat and polymeric solids; pressure buildup may occur in closed containers.
Response guidance: For a UN 2328 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 156. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff, dust or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2328 should emphasize isocyanate respiratory sensitization, water reaction/CO2 pressure, vapor monitoring, PPE, decontamination and runoff containment. Use ERG 156, SDS and local SOP.
Regulatory context: Trimethylhexamethylene diisocyanate 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: Trimethylhexamethylene diisocyanate should be stored in tightly closed compatible containers in a cool, dry, ventilated area away from water/moisture, amines, alcohols, acids/bases where incompatible and heat. Prevent pressure buildup and humid air exposure.
UN 2328 Quick Details
Common Hazards of UN 2328
- TOXIC isocyanate liquid; inhalation of vapor or aerosol may cause severe respiratory sensitization and injury.
- Combustible material: may burn but does not ignite readily.
- Reacts with water to release carbon dioxide, heat and polymeric solids; pressure buildup may occur in closed containers.
- Skin and eye contact may cause irritation, burns or sensitization.
- Vapors may collect in low or confined areas depending on temperature and formulation.
- Fire may produce nitrogen oxides, isocyanate vapors, hydrogen cyanide-type products and other toxic gases.
- Runoff may spread toxic isocyanate contamination.
Chemical Identity & Physical Properties
Clear to pale yellow liquid with a sharp, pungent odor characteristic of isocyanates. Liquid at room temperature.
| Also known as | TMDITrimethylhexamethylene-1,6-diisocyanate2,2,4-trimethylhexamethylene diisocyanateTMH diisocyanate1,6-diisocyanato-2,2,4-trimethylhexane |
| CAS Number | 15646-96-5 |
| Appearance | Clear to pale yellow liquid with a sharp, pungent odor characteristic of isocyanates. Liquid at room temperature. |
| Flash Point | 127C (261F) |
| Boiling Point | Approximately 255-270C (491-518F) with decomposition |
| Vapor Density | 8.3 (much heavier than air) |
| Water Reactivity | Reacts slowly with water releasing carbon dioxide gas; may cause foaming and heat generation. Avoid direct water contact. |
Fireground Response Guidance — UN 2328
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, aerosol, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS; Level A may be needed for heavy vapor or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 2328 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, dust, mist, smoke or fumes and avoid skin or eye contact.
- Avoid unnecessary water contact with released product unless incident command confirms a compatible control use.
- Do not touch damaged containers or 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 release area and expand the perimeter for fire involvement, vapor spread, dust generation, water reaction or unknown product identity.
- Use ERG Guide 156, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2328 — Trimethylhexamethylene diisocyanateUse 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.