UN 2329 — Trimethyl phosphite
Placard: Flammable. ERG Guide 130. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2329 is Trimethyl phosphite, a flammable liquid with toxic or corrosive exposure concerns assigned to ERG Guide 130. Vapors can flash back and runoff can spread contamination.
Hazard overview: FLAMMABLE liquid with toxic or corrosive exposure concerns; vapors may ignite and form explosive mixtures with air. Vapors are heavier than air and may travel to ignition sources and flash back. Liquid or vapor may irritate or burn eyes, skin and respiratory tissue depending on product.
Response guidance: For a UN 2329 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 130. 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 2329 should emphasize vapor travel, sewer flashback, foam selection, container cooling, ignition control, toxic/corrosive exposure where applicable and runoff containment. Use ERG 130, SDS and local SOP.
Regulatory context: Trimethyl phosphite 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: Trimethyl phosphite should be stored in approved flammable-liquid containers with ventilation, bonding/grounding where required, spill containment and separation from heat, ignition sources, oxidizers and incompatible materials.
UN 2329 Quick Details
Common Hazards of UN 2329
- FLAMMABLE liquid with toxic or corrosive exposure concerns; vapors may ignite and form explosive mixtures with air.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Liquid or vapor may irritate or burn eyes, skin and respiratory tissue depending on product.
- Runoff to sewers may create fire, explosion and toxic/corrosive contamination hazards.
- Containers may rupture or explode when heated.
- Fire may produce nitrogen oxides, phosphorus oxides or other irritating/toxic gases depending on material.
- Specific isomer or formulation hazards should be confirmed from SDS.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, fruity odor. Mobile liquid at room temperature.
| Also known as | TrimethoxyphosphinePhosphorous acid trimethyl esterMethyl phosphiteTMP |
| CAS Number | 121-45-9 |
| Appearance | Colorless to pale yellow liquid with a pungent, fruity odor. Mobile liquid at room temperature. |
| Flash Point | 26°C (79°F) |
| Boiling Point | 111-112°C (232-234°F) |
| Vapor Density | 4.3 (heavier than air) |
| Water Reactivity | Hydrolyzes slowly in water, forming methanol and phosphorous acid; reaction accelerates with heat |
Fireground Response Guidance — UN 2329
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves, eye/face protection, flame-resistant protection as appropriate and PPE selected from SDS.
Isolation & Evacuation
First Actions for a UN 2329 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.
- Eliminate ignition sources if safe and keep vapors and runoff out of drains, sewers, basements and low areas.
- 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 130, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2329 — Trimethyl phosphiteUse 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.