☣️ UN 3374 • CLASS 2
UN 3374 — Acetylene, solvent free
Placard: Flammable Gas. ERG Guide 116. 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 3374 is Acetylene, solvent free, assigned to ERG Guide 116. First responders should verify the shipping papers and SDS, isolate the area, and base entry, PPE and control tactics on the product's listed hazards.
Hazard overview: The main hazard is extreme flammability and cylinder rupture. Acetylene can form explosive mixtures and may react explosively under heat or contamination.
Response guidance: For UN 3374, eliminate ignition sources, stop gas flow only if safe, cool cylinders from maximum distance, and evacuate if a cylinder is heated, leaking or exposed to flame.
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UN 3374 Quick Details
UN 3374
Product name: Acetylene, solvent free
DOT Class: 2
Placard type: Flammable Gas
ERG Guide: 116 (check current ERG)
Initial isolation: ERG 116: isolate 800m all directions for large spills; evacuate 1600m downwind if cylinder fire or leak; may explode from heat or contamination even without air
Common Hazards of UN 3374
- EXTREMELY FLAMMABLE.
- Will be easily ignited by heat, sparks or flames.
- Will form explosive mixtures with air. Acetylene may react explosively under heat, pressure or contamination.
- Disilane (UN3553) and Silane (UN2203) will ignite spontaneously in air and may re-ignite.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Vapors may travel to source of ignition and flash back.
- Cylinders exposed to fire may vent and release flammable gas through pressure relief devices.
Chemical Identity & Physical Properties
Colorless gas with a sweet, ethereal odor when pure; commercial grade has a garlic-like odor due to impurities. Shipped dissolved in acetone or dimethylformamide in cylinders.
| Also known as | EthyneEthineNarcylenVinylene |
| CAS Number | 74-86-2 |
| Appearance | Colorless gas with a sweet, ethereal odor when pure; commercial grade has a garlic-like odor due to impurities. Shipped dissolved in acetone or dimethylformamide in cylinders. |
| Flash Point | Not applicable (gas); autoignition temperature 305C (581F) |
| Boiling Point | -84C (-119F) at atmospheric pressure |
| Vapor Density | 0.91 (lighter than air) |
| Water Reactivity | No significant reaction with water; slightly soluble |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3374
Extinguishing Media
Do not use water or foam; use CO2 or dry chemical; stop flow of gas if possible
PPE Requirements
⚠️ Level B minimum; SCBA with full protective clothing required; avoid all ignition sources
Level B minimum; SCBA with full protective clothing required; avoid all ignition sources.
Isolation & Evacuation
ERG 116: isolate 800m all directions for large spills; evacuate 1600m downwind if cylinder fire or leak; may explode from heat or contamination even without air
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 116).
First Actions for a UN 3374 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.
- Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
- Consider initial downwind evacuation for at least 800 meters (1/2 mile).
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📋 Copy & Share Field Card
UN 3374 — Acetylene, solvent freeHAZMAT RADIO NOTE — UN 3374
Product: Acetylene, solvent free
Class 2 / Flammable Gas / ERG 116
PPE: Level B minimum; SCBA with full protective clothing required; avoid all ignition sources
ISOLATION: ERG 116: isolate 800m all directions for large spills; evacuate 1600m downwind if cylinder fire or leak; may explode from heat or contamination even without air
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 3374 — Acetylene, solvent free
Class: 2 | Placard: Flammable Gas | ERG Guide: 116
Appearance: Colorless gas with a sweet, ethereal odor when pure; commercial grade has a garlic-like odor due to impurities. Shipped dissolved in acetone or dimethylformamide in cylinders.
Water Reactivity: No significant reaction with water; slightly soluble
Extinguishing: Do not use water or foam; use CO2 or dry chemical; stop flow of gas if possible
PPE: Level B minimum; SCBA with full protective clothing required; avoid all ignition sources
Isolation: ERG 116: isolate 800m all directions for large spills; evacuate 1600m downwind if cylinder fire or leak; may explode from heat or contamination even without air
— Key Hazards —
• EXTREMELY FLAMMABLE.
• Will be easily ignited by heat, sparks or flames.
• Will form explosive mixtures with air. Acetylene may react explosively under heat, pressure or contamination.
— 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.
• Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
SOURCE: allfirefighter.com/hazmat/un/acetylene-solvent-free-un-3374 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3374 Acetylene, solvent free Cls2 ERG116 | allfirefighter.com/hazmat/un/acetylene-solvent-free-un-3374SMS / 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/acetylene-solvent-free-un-3374
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Frequently Asked Questions about UN 3374
UN 3374 is Acetylene, solvent free. It is assigned to ERG Guide 116 for initial emergency response.
Yes. Acetylene can ignite easily, form explosive mixtures with air and react explosively under heat or contamination.
Evacuate, cool from maximum distance when safe and do not approach a cylinder exposed to flame or heavy heat.
Stop the gas flow if safe. Use dry chemical or CO2 for small fires and cool nearby cylinders from a protected position.
Use SCBA with full protective clothing and avoid all ignition sources during leak or fire response.
Yes. Vapors may travel to an ignition source and flash back, so ignition control and isolation are critical.
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.