UN 2398 — Methyl tert-butyl ether
Placard: Flammable. ERG Guide 127. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2398 is Methyl tert-butyl ether, a highly flammable ether assigned to ERG Guide 127. Heavy vapor flashback and storage-history review are important.
Hazard overview: HIGHLY FLAMMABLE ether 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. Ether vapors can accumulate in drains, basements and confined areas.
Response guidance: For UN 2398, 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 using SDS and ERG 127.
Firefighter training notes: Training for UN 2398 should emphasize ether/peroxide storage review where applicable, vapor travel, sewer flashback, foam selection, ignition control and container cooling. Use ERG 127, SDS and local SOP.
Regulatory context: Methyl tert-butyl ether 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: Methyl tert-butyl ether should be stored in approved flammable-liquid containers with ventilation and ignition control. Track age, inhibitor or peroxide concerns where required by SDS and facility SOP.
UN 2398 Quick Details
Common Hazards of UN 2398
- HIGHLY FLAMMABLE ether 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.
- Ether vapors can accumulate in drains, basements and confined areas.
- Some ethers may form explosive peroxides during storage; verify age, inhibitor status and SDS.
- 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
Colorless liquid with a distinctive ether-like or terpene-like odor. Volatile and highly flammable at ambient temperatures.
| Also known as | MTBEtert-Butyl methyl ether2-Methoxy-2-methylpropaneMethyl t-butyl etherDriveron |
| CAS Number | 1634-04-4 |
| Appearance | Colorless liquid with a distinctive ether-like or terpene-like odor. Volatile and highly flammable at ambient temperatures. |
| Flash Point | -28°C (-18°F) |
| Boiling Point | 55°C (131°F) |
| Vapor Density | 3.1 (heavier than air) |
| Water Reactivity | No significant reaction; slightly soluble in water (approximately 4-5% by weight) |
Fireground Response Guidance — UN 2398
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 2398 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 2398 — Methyl tert-butyl etherUse 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.