☣️ UN 3501 • CLASS 2
Chemical under pressure, flammable, n.o.s.
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 3501
Class: 2
Placard type: Flammable Gas
ERG: Guide 115 (check current ERG)
Isolation: ERG 115: Initial isolation 100m in all directions; protective action distance 300m downwind for large spills during day, 800m at night
Chemical & Response Details
| Also known as | Chemical under pressure flammable NOSPressurized flammable chemicalAerosol flammable chemicalCompressed flammable chemical mixture |
| Appearance | Variable appearance depending on specific chemical; typically a pressurized liquid or gas stored in containers under pressure at room temperature. May be colorless to colored liquid/gas with various odors depending on contents. |
| Flash Point | Variable, typically below -18C (0F) for flammable gases or highly flammable liquids under pressure |
| Boiling Point | Variable depending on specific chemical contents and pressure conditions |
| Vapor Density | Variable, typically heavier than air for most flammable gases and vapors under pressure |
| Water Reactivity | Variable depending on specific chemical; many show no significant water reaction, but some flammable gases or chemicals may react |
| Extinguishing | Dry chemical, CO2, or foam appropriate for flammable liquids/gases; water spray for cooling containers only |
| PPE | ⚠️ Level B minimum with SCBA required; full protective clothing and respiratory protection mandatory due to flammability and pressure release hazards |
| Isolation | ERG 115: Initial isolation 100m in all directions; protective action distance 300m downwind for large spills during day, 800m at night |
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.
- 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.
- Containers may explode when heated.
- Ruptured cylinders may rocket.
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 3501 — Chemical under pressure, flammable, n.o. HAZMAT RADIO NOTE — UN 3501
Product: Chemical under pressure, flammable, n.o.s.
Class 2 / Flammable Gas / ERG 115
PPE: Level B minimum with SCBA required; full protective clothing and respiratory protection mandatory due to flammability and pressure release hazards
ISOLATION: ERG 115: Initial isolation 100m in all directions; protective action distance 300m downwind for large spills during day, 800m at night
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 3501 — Chemical under pressure, flammable, n.o.s.
Class: 2 | Placard: Flammable Gas | ERG Guide: 115
Appearance: Variable appearance depending on specific chemical; typically a pressurized liquid or gas stored in containers under pressure at room temperature. May be colorless to colored liquid/gas with various odors depending on contents.
Water Reactivity: Variable depending on specific chemical; many show no significant water reaction, but some flammable gases or chemicals may react
Extinguishing: Dry chemical, CO2, or foam appropriate for flammable liquids/gases; water spray for cooling containers only
PPE: Level B minimum with SCBA required; full protective clothing and respiratory protection mandatory due to flammability and pressure release hazards
Isolation: ERG 115: Initial isolation 100m in all directions; protective action distance 300m downwind for large spills during day, 800m at night
— Key Hazards —
• EXTREMELY FLAMMABLE.
• Will be easily ignited by heat, sparks or flames.
• Will form explosive mixtures with air.
— 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/3501 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3501 Chemical under pressure, flammable, n.o.s. Cls2 ERG115 | allfirefighter.com/hazmat/un/3501SMS / 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/3501
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FAQ
EXTREMELY FLAMMABLE. Will be easily ignited by heat, sparks or flames. Will form explosive mixtures with air. 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. Containers may explode when heated. Ruptured cylinders may rocket.
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 with SCBA required; full protective clothing and respiratory protection mandatory due to flammability and pressure release hazards
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 115 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.