☣️ UN 3500 • CLASS 2
Chemical under pressure, 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 3500
Class: 2
Placard type: Non-Flammable Gas
ERG: Guide 126 (check current ERG)
Isolation: ERG 126: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m in all directions and consider evacuation for 800m in all directions
Chemical & Response Details
| Also known as | Chemical under pressure NOSCompressed chemicalPressurized chemical mixtureChemical aerosol |
| Appearance | Variable appearance depending on specific chemical; typically a liquid or gas under pressure in cylinders or aerosol containers at room temperature. May have various colors and odors depending on contents. |
| Flash Point | Variable depending on specific chemical; some may be flammable while others are non-flammable |
| Boiling Point | Variable depending on specific chemical and pressure conditions |
| Vapor Density | Variable depending on specific chemical; may be heavier or lighter than air |
| Water Reactivity | Variable depending on specific chemical; consult SDS for specific contents |
| Extinguishing | Variable; dry chemical, CO2, or water spray may be appropriate depending on specific chemical contents |
| PPE | ⚠️ Level B minimum recommended; SCBA and chemical-resistant suit required; consult specific chemical contents for exact PPE requirements |
| Isolation | ERG 126: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m in all directions and consider evacuation for 800m in all directions |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
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 3500 — Chemical under pressure, n.o.s. HAZMAT RADIO NOTE — UN 3500
Product: Chemical under pressure, n.o.s.
Class 2 / Non-Flammable Gas / ERG 126
PPE: Level B minimum recommended; SCBA and chemical-resistant suit required; consult specific chemical contents for exact PPE requirements
ISOLATION: ERG 126: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m in all directions and consider evacuation for 800m in all directions
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 3500 — Chemical under pressure, n.o.s.
Class: 2 | Placard: Non-Flammable Gas | ERG Guide: 126
Appearance: Variable appearance depending on specific chemical; typically a liquid or gas under pressure in cylinders or aerosol containers at room temperature. May have various colors and odors depending on contents.
Water Reactivity: Variable depending on specific chemical; consult SDS for specific contents
Extinguishing: Variable; dry chemical, CO2, or water spray may be appropriate depending on specific chemical contents
PPE: Level B minimum recommended; SCBA and chemical-resistant suit required; consult specific chemical contents for exact PPE requirements
Isolation: ERG 126: Initial isolation 100m in all directions; if tank/rail car involved in fire, isolate 800m in all directions and consider evacuation for 800m in all directions
— Key Hazards —
• Some may burn but none ignite readily.
• Containers may explode when heated.
• Ruptured cylinders may rocket.
— 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/3500 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3500 Chemical under pressure, n.o.s. Cls2 ERG126 | allfirefighter.com/hazmat/un/3500SMS / 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/3500
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FAQ
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.
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 recommended; SCBA and chemical-resistant suit required; consult specific chemical contents for exact PPE requirements
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 126 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.