☣️ UN 3156 • CLASS 2
Compressed gas, oxidizing, n.o.s.
Placard: Non-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 3156
Class: 2
Placard type: Non-Flammable Gas
ERG: Guide 122 (check current ERG)
Isolation: ERG 122: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation
Chemical & Response Details
| Also known as | Oxidizing compressed gas N.O.S.Compressed oxidizing gasOxidizer compressed gas not otherwise specified |
| Appearance | Colorless to variably colored compressed gas depending on specific oxidizer. Odor varies by specific substance. Stored under pressure in cylinders or tanks at room temperature. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | Not applicable (compressed gas, varies by specific oxidizer) |
| Vapor Density | Varies by specific oxidizer (typically heavier than air) |
| Water Reactivity | Generally no significant reaction, though specific oxidizers may vary |
| Extinguishing | Do not use foam; use water spray to cool containers, keep combustibles away |
| PPE | ⚠️ Level B minimum; SCBA required; chemical-resistant suit if liquid contact possible during release |
| Isolation | ERG 122: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Substance does not burn but will support combustion.
- Some may react explosively with fuels.
- May ignite combustibles (wood, paper, oil, clothing, etc.).
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Runoff may create fire or explosion hazard.
- Containers may explode when heated.
- Ruptured cylinders may rocket.
- Vapors may cause dizziness or asphyxiation without warning, especially when in closed or confined areas.
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
- 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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UN 3156 — Compressed gas, oxidizing, n.o.s. HAZMAT RADIO NOTE — UN 3156
Product: Compressed gas, oxidizing, n.o.s.
Class 2 / Non-Flammable Gas / ERG 122
PPE: Level B minimum; SCBA required; chemical-resistant suit if liquid contact possible during release
ISOLATION: ERG 122: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation
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 3156 — Compressed gas, oxidizing, n.o.s.
Class: 2 | Placard: Non-Flammable Gas | ERG Guide: 122
Appearance: Colorless to variably colored compressed gas depending on specific oxidizer. Odor varies by specific substance. Stored under pressure in cylinders or tanks at room temperature.
Water Reactivity: Generally no significant reaction, though specific oxidizers may vary
Extinguishing: Do not use foam; use water spray to cool containers, keep combustibles away
PPE: Level B minimum; SCBA required; chemical-resistant suit if liquid contact possible during release
Isolation: ERG 122: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation
— Key Hazards —
• Substance does not burn but will support combustion.
• Some may react explosively with fuels.
• May ignite combustibles (wood, paper, oil, clothing, etc.).
— 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/3156 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3156 Compressed gas, oxidizing, n.o.s. Cls2 ERG122 | allfirefighter.com/hazmat/un/3156SMS / 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/3156
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FAQ
Substance does not burn but will support combustion. Some may react explosively with fuels. May ignite combustibles (wood, paper, oil, clothing, etc.). Vapors from liquefied gas are initially heavier than air and spread along ground. Runoff may create fire or explosion hazard. Containers may explode when heated. Ruptured cylinders may rocket. Vapors may cause dizziness or asphyxiation without warning, especially when in closed or confined areas.
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 required; chemical-resistant suit if liquid contact possible during release
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 122 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.