☣️ UN 3374 • CLASS 2
Acetylene, solvent free
Placard: Flammable Gas. 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.
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Quick details
UN 3374
Class: 2
Placard type: Flammable Gas
ERG: Guide 116 (check current ERG)
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
Chemical & Response Details
| 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 |
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- EXTREMELY FLAMMABLE.
- Will be easily ignited by heat, sparks or flames.
- Will form explosive mixtures with air. Acetylene (UN1001, UN3374) may react explosively even in the
- 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.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- 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
- 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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UN 3374 — Acetylene, solvent free HAZMAT 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 (UN1001, UN3374) may react explosively even in the
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• 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/3374 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3374 Acetylene, solvent free Cls2 ERG116 | allfirefighter.com/hazmat/un/3374SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/3374
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FAQ
EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. Acetylene (UN1001, UN3374) may react explosively even in the 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.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum; SCBA with full protective clothing required; avoid all ignition sources
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 116 and your department SOP/SOG for incident-specific protective actions.
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.