☣️ UN 1166 • CLASS 3

UN 1166 — Dioxolane

Placard: Flammable. ERG Guide 127. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.

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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.

UN 1166 is Dioxolane, a Class 3 flammable ether liquid assigned to ERG Guide 127. It can produce vapors that ignite easily and may present peroxide concerns if old or improperly stored.

Hazard overview: UN 1166 presents flammable vapor, flashback and potential peroxide-related handling hazards. Vapors are heavier than air and can collect in low or sewer areas; old containers should not be disturbed until assessed through SDS and specialist guidance.

Response guidance: For a UN 1166 incident, responders should confirm the product using shipping papers, container markings, SDS and ERG Guide 127. Establish incident command, isolate the area, stay upwind and uphill, remove ignition sources when safe, keep vapors or runoff out of sewers and use compatible Class B fire-control agents from a protected position.

Firefighter training notes: Training for UN 1166 should emphasize ether vapor flashback, low-area vapor accumulation, sewer explosion hazards and possible peroxide issues in old containers. Common errors include disturbing suspect containers and ignoring ignition sources.

Regulatory context: Dioxolane is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.

Storage & handling: Dioxolane should be stored in tightly closed compatible containers in a cool, dry, well-ventilated flammable-liquid area, away from heat, ignition sources and oxidizers. Follow SDS guidance for peroxide-forming ether storage, shelf-life checks and inhibitor requirements where applicable.

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UN 1166 Quick Details

UN 1166
Product name: Dioxolane
DOT Class: 3
Placard type: Flammable
ERG Guide: 127 (check current ERG)
Initial isolation: ERG 127: Small spill isolate 30m all directions; large spill isolate 150m all directions, evacuate 800m downwind if tank/rail car involved in fire

Common Hazards of UN 1166

  • HIGHLY FLAMMABLE ether or cyclic ether liquid; vapors may ignite easily.
  • Vapors may form explosive mixtures with air and flash back to the source.
  • Vapors are heavier than air and may collect in low, confined or sewer areas.
  • Some ethers can form peroxides during storage; verify age, stabilizer and SDS before handling suspect containers.
  • Fire may produce irritating or toxic combustion products.
  • Runoff to sewer may create fire or explosion hazards.
  • Containers may rupture or explode when heated.

Chemical Identity & Physical Properties

Colorless liquid with a mild, ether-like odor. Exists as a mobile liquid at room temperature with low viscosity.

Also known as1,3-Dioxolane1,3-DioxacyclopentaneEthylene glycol formalGlycol methylene ether
CAS Number646-06-0
AppearanceColorless liquid with a mild, ether-like odor. Exists as a mobile liquid at room temperature with low viscosity.
Flash Point2°C (36°F)
Boiling Point78°C (172°F)
Vapor Density2.6 (heavier than air)
Water ReactivityNo significant reaction with water; miscible in water
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.

Fireground Response Guidance — UN 1166

Extinguishing Media

Use alcohol-resistant foam, dry chemical or CO2 when compatible; water spray may be used from a protected position to cool exposed containers.

PPE Requirements

⚠️ Level B minimum with SCBA required in vapor areas; full chemical-resistant suit for spill response

Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves and splash protection selected from SDS, and treat old or suspect ether containers cautiously because of possible peroxide concerns.

Isolation & Evacuation

ERG 127: Small spill isolate 30m all directions; large spill isolate 150m all directions, evacuate 800m downwind if tank/rail car involved in fire
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 127).

First Actions for a UN 1166 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.
  • Eliminate ignition sources if it is safe to do so.
  • Do not touch or walk through spilled liquid unless properly trained and wearing appropriate protective equipment.
  • Ventilate closed spaces before entering, but only if properly trained, equipped and authorized by incident command.
  • Isolate the spill or leak area for at least 50 meters (150 feet) in all directions.
  • For large spills, fire involvement or strong vapor movement, expand isolation and consider downwind evacuation based on monitoring and incident command.
  • Use ERG Guide 127, shipping papers, SDS and local SOP for protective actions and entry decisions.
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📋 Copy & Share Field Card

UN 1166 — Dioxolane
HAZMAT RADIO NOTE — UN 1166 Product: Dioxolane Class 3 / Flammable / ERG 127 PPE: Level B minimum with SCBA required in vapor areas; full chemical-resistant suit for spill response ISOLATION: ERG 127: Small spill isolate 30m all directions; large spill isolate 150m all directions, evacuate 800m downwind if tank/rail car involved in fire ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO

Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.

SMS WhatsApp
=== IC HAZMAT BRIEFING === UN 1166 — Dioxolane Class: 3 | Placard: Flammable | ERG Guide: 127 Appearance: Colorless liquid with a mild, ether-like odor. Exists as a mobile liquid at room temperature with low viscosity. Water Reactivity: No significant reaction with water; miscible in water Extinguishing: Use alcohol-resistant foam, dry chemical or CO2 when compatible; water spray may be used from a protected position to cool exposed containers. PPE: Level B minimum with SCBA required in vapor areas; full chemical-resistant suit for spill response Isolation: ERG 127: Small spill isolate 30m all directions; large spill isolate 150m all directions, evacuate 800m downwind if tank/rail car involved in fire — Key Hazards — • HIGHLY FLAMMABLE ether or cyclic ether liquid; vapors may ignite easily. • Vapors may form explosive mixtures with air and flash back to the source. • Vapors are heavier than air and may collect in low, confined or sewer areas. — First Actions — • 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. • Eliminate ignition sources if it is safe to do so. SOURCE: allfirefighter.com/hazmat/un/dioxolane-un-1166 | Always use current ERG + SOP/SOGIC BRIEFING

Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.

SMS (short)
UN1166 Dioxolane Cls3 ERG127 | ERG 127: Small spill isolate 30m all directions; large spill isolate 150m all di | allfirefighter.com/hazmat/un/dioxolane-un-1166SMS / 160 CHAR

Use for: Quick text to command or incoming units. Fits in a single SMS.

⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/dioxolane-un-1166

Related UN Numbers in Class 3

Discovery block for training / quick reference. Always consult the current ERG + your SOP/SOG for operations.
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Frequently Asked Questions about UN 1166

UN 1166 is Dioxolane, a hazardous material assigned to ERG Guide 127.

Yes. It is flammable and vapors may form explosive mixtures with air.

ERG Guide 127 applies to UN 1166 and should be used for initial isolation, protective actions and first response guidance.

UN 1166 presents flammable vapor, flashback and potential peroxide-related handling hazards. Vapors are heavier than air and can collect in low or sewer areas; old containers should not be disturbed until assessed through SDS and specialist guidance.

Use positive-pressure SCBA for vapor, fire or confined-space exposure. Wear chemical-resistant gloves and splash protection selected from SDS, and treat old or suspect ether containers cautiously because of possible peroxide concerns.

Responders should isolate the area, stay upwind and uphill, eliminate ignition sources when safe, prevent sewer entry, verify the product with SDS and follow ERG Guide 127, incident command and local SOP.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.