UN 2376 — 2,3-Dihydropyran
Placard: Flammable. ERG Guide 127. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2376 is 2,3-Dihydropyran, a highly flammable ether/acetal liquid assigned to ERG Guide 127. Heavy vapor flashback and storage-history review are important.
Hazard overview: HIGHLY FLAMMABLE ether/acetal liquid; vapors may ignite easily and form explosive mixtures with air. Vapors are heavier than air and may travel to ignition sources and flash back. Vapor explosion hazard exists in drains, basements and confined areas.
Response guidance: For UN 2376, isolate the area, eliminate ignition sources, keep vapors out of drains and use SCBA in vapor or fire conditions. Cool containers from a protected distance and choose foam, dry chemical or CO2 based on SDS and ERG 127.
Firefighter training notes: Training for UN 2376 should emphasize vapor travel, low-area accumulation, sewer flashback, foam selection, ignition control, container cooling and vapor monitoring. Use ERG 127, SDS and local SOP.
Regulatory context: 2,3-Dihydropyran 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: 2,3-Dihydropyran should be stored in approved flammable-liquid containers with ventilation and ignition control. Track age, inhibitor or oxidation/peroxide concerns where required by SDS and facility SOP.
UN 2376 Quick Details
Common Hazards of UN 2376
- HIGHLY FLAMMABLE ether/acetal liquid; vapors may ignite easily and form explosive mixtures with air.
- Vapors are heavier than air and may travel to ignition sources and flash back.
- Vapor explosion hazard exists in drains, basements and confined areas.
- Some ether/acetal materials may hydrolyze slowly or form unstable oxidation products; verify SDS and storage history.
- Runoff to sewers may create fire or explosion hazards.
- Fire may produce irritating and/or toxic smoke.
- Containers may rupture or explode when heated.
Chemical Identity & Physical Properties
Clear, colorless liquid with a characteristic ethereal or sweet odor at room temperature.
| Also known as | 2,3-Dihydro-2H-pyranDHP2H-3,4-DihydropyranDelta-5,6-dihydropyran |
| CAS Number | 110-87-2 |
| Appearance | Clear, colorless liquid with a characteristic ethereal or sweet odor at room temperature. |
| Flash Point | -18°C (0°F) |
| Boiling Point | 86°C (187°F) |
| Vapor Density | 2.9 (heavier than air) |
| Water Reactivity | Slightly soluble in water; no violent reaction but may hydrolyze slowly in aqueous conditions |
Fireground Response Guidance — UN 2376
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves, eye/face protection and flame-resistant protection as appropriate.
Isolation & Evacuation
First Actions for a UN 2376 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; keep responders out of low vapor areas.
- Eliminate ignition sources if this can be done safely.
- Avoid breathing vapor, mist or smoke and avoid skin or eye contact.
- 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 127, SDS, shipping papers and air monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2376 — 2,3-DihydropyranUse 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.