☣️ UN 3299 • CLASS 2
UN 3299 — Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide
Placard: Non-Flammable Gas. ERG Guide 126. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ Verification required:
Broad or variable material category; verify exact product, SDS and shipping papers.
⚠️ 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.
Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide is a compressed sterilant gas mixture containing ethylene oxide at limited concentration. It is still treated as toxic and potentially carcinogenic during leaks.
Hazard overview: Ethylene oxide mixtures may not ignite readily in this classification, but heated cylinders can rupture. Released gas can displace air and expose responders to toxic EtO vapors.
Response guidance: Isolate the cylinder or leak area, stay upwind, ventilate cautiously and protect containers from heat. Use SCBA and chemical protective clothing for leak control or rescue near the release.
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UN 3299 Quick Details
UN 3299
Product name: Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide
DOT Class: 2
Placard type: Non-Flammable Gas
ERG Guide: 126 (check current ERG)
Initial isolation: ERG 126: Initial isolation 100m all directions; protective action distance 300m downwind (small spill day), 800m (large spill night); evacuate area if container rupture imminent
Common Hazards of UN 3299
- Some may burn but none ignite readily.
- Containers may explode when heated.
- Ruptured cylinders may rocket.
- Vapors may cause dizziness or asphyxiation without warning, especially when in closed or confined areas.
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
- Fire may produce irritating, corrosive and/or toxic gases.
Chemical Identity & Physical Properties
Colorless liquefied gas mixture under pressure. Ethylene oxide component has a sweet ether-like odor at high concentrations; tetrafluoroethane (R-134a) is nearly odorless. Stored as compressed liquid, releases as gas at ambient temperature.
| Also known as | ETO/R-134a mixtureEthylene oxide-tetrafluoroethane blendEO-HFC134a sterilant mixture |
| Appearance | Colorless liquefied gas mixture under pressure. Ethylene oxide component has a sweet ether-like odor at high concentrations; tetrafluoroethane (R-134a) is nearly odorless. Stored as compressed liquid, releases as gas at ambient temperature. |
| Flash Point | Not applicable (compressed gas mixture) |
| Boiling Point | Approximately -26C (-15F) for R-134a component; -10.7C (12.7F) for ethylene oxide component |
| Vapor Density | 3.5-3.8 (heavier than air) |
| Water Reactivity | No significant reaction with water; gas will dissolve slightly |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3299
Extinguishing Media
CO2, dry chemical, water spray for cooling containers; foam generally not needed for gas
PPE Requirements
⚠️ Level B minimum with SCBA mandatory; ethylene oxide is highly toxic by inhalation and carcinogenic; chemical-resistant gloves and suit required
Level B minimum with SCBA mandatory; ethylene oxide is highly toxic by inhalation and carcinogenic; chemical-resistant gloves and suit required.
Isolation & Evacuation
ERG 126: Initial isolation 100m all directions; protective action distance 300m downwind (small spill day), 800m (large spill night); evacuate area if container rupture imminent
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 126).
First Actions for a UN 3299 Incident
- CALL 911, then contact the emergency response telephone number shown on shipping papers, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Many gases are heavier than air and will spread along the ground and collect in low or confined areas.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
- Consider initial downwind evacuation for at least 500 meters (1/3 mile).
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📋 Copy & Share Field Card
UN 3299 — Ethylene oxide and tetrafluoroethane mixHAZMAT RADIO NOTE — UN 3299
Product: Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide
Class 2 / Non-Flammable Gas / ERG 126
PPE: Level B minimum with SCBA mandatory; ethylene oxide is highly toxic by inhalation and carcinogenic; chemical-resistant gloves and suit required
ISOLATION: ERG 126: Initial isolation 100m all directions; protective action distance 300m downwind (small spill day), 800m (large spill night); evacuate area if container rupture imminent
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3299 — Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide
Class: 2 | Placard: Non-Flammable Gas | ERG Guide: 126
Appearance: Colorless liquefied gas mixture under pressure. Ethylene oxide component has a sweet ether-like odor at high concentrations; tetrafluoroethane (R-134a) is nearly odorless. Stored as compressed liquid, releases as gas at ambient temperature.
Water Reactivity: No significant reaction with water; gas will dissolve slightly
Extinguishing: CO2, dry chemical, water spray for cooling containers; foam generally not needed for gas
PPE: Level B minimum with SCBA mandatory; ethylene oxide is highly toxic by inhalation and carcinogenic; chemical-resistant gloves and suit required
Isolation: ERG 126: Initial isolation 100m all directions; protective action distance 300m downwind (small spill day), 800m (large spill night); evacuate area if container rupture imminent
— Key Hazards —
• Some may burn but none ignite readily.
• Containers may explode when heated.
• Ruptured cylinders may rocket.
— First Actions —
• CALL 911, then contact the emergency response telephone number shown on shipping papers, if available.
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Many gases are heavier than air and will spread along the ground and collect in low or confined areas.
SOURCE: allfirefighter.com/hazmat/un/ethylene-oxide-and-tetrafluoroethane-un-3299 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3299 Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide Cls2 ERG126 | allfirefighter.com/hazmat/un/ethylene-oxide-and-tetrafluoroethane-un-3299SMS / 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/ethylene-oxide-and-tetrafluoroethane-un-3299
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Frequently Asked Questions about UN 3299
UN 3299 is Ethylene oxide and tetrafluoroethane mixture, with not more than 5.6% ethylene oxide, assigned to ERG Guide 126 and placarded as Non-Flammable Gas.
Yes. Ethylene oxide R-134a mixture presents a serious toxic exposure hazard; avoid inhalation, ingestion, skin contact and contaminated runoff.
Yes, corrosive effects are possible. Avoid skin and eye contact and use chemical-resistant protection.
Gas can spread downwind, collect in low or confined areas, displace oxygen or create toxic exposure depending on the material.
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.