☣️ UN 3502 • CLASS 2
UN 3502 — Chemical under pressure, poisonous, n.o.s.
Placard: Non-Flammable Gas. ERG Guide 123. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ Verification required:
Broad or variable material category; verify exact product, SDS and shipping papers.
⚠️ 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 3502 is Chemical under pressure, poisonous, n.o.s., a pressurized hazardous material assigned to ERG Guide 123. The exact contents should be verified from shipping papers and the SDS before close-range action.
Hazard overview: Primary hazards include toxic exposure, corrosive burns, fire or vapor ignition, container rupture. Chemical under pressure, poisonous, n.o.s. may release irritating, toxic or corrosive vapors when heated, spilled or involved in fire, so avoid contact, inhalation and incompatible materials.
Response guidance: For a UN 3502 incident, establish incident command, isolate the area, stay upwind and uphill, keep unauthorized personnel away, verify shipping papers/SDS and follow ERG 123. Use extinguishing, cooling, containment and decontamination tactics only when compatible with the material and local SOP.
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UN 3502 Quick Details
UN 3502
Product name: Chemical under pressure, poisonous, n.o.s.
DOT Class: 2
Placard type: Non-Flammable Gas
ERG Guide: 123 (check current ERG)
Initial isolation: ERG 123: Isolate spill/leak area immediately for at least 100m in all directions; initial evacuation 800m downwind if large spill
Common Hazards of UN 3502
- TOXIC; may be fatal if inhaled or absorbed through skin.
- Vapors may be irritating and/or corrosive.
- Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may cause environmental contamination.
- Some may burn but none ignite readily.
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Cylinders exposed to fire may vent and release toxic and/or corrosive gas through pressure relief
Chemical Identity & Physical Properties
Not otherwise specified (n.o.s.) entry covering various toxic chemicals under pressure. May be gas, liquefied gas, or dissolved gas. Physical characteristics vary by specific chemical.
| Also known as | Chemical under pressure poisonous NOSCompressed poisonous chemical NOSPressurized toxic chemical NOS |
| Appearance | Not otherwise specified (n.o.s.) entry covering various toxic chemicals under pressure. May be gas, liquefied gas, or dissolved gas. Physical characteristics vary by specific chemical. |
| Flash Point | Variable depending on specific chemical; refer to SDS |
| Boiling Point | Variable depending on specific chemical; refer to SDS |
| Vapor Density | Variable depending on specific chemical; typically heavier than air for pressurized gases |
| Water Reactivity | Variable depending on specific chemical; may range from no reaction to violent reactivity |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3502
Extinguishing Media
Do not use water spray; use dry chemical, CO2, or inert gas as appropriate for specific chemical
PPE Requirements
⚠️ Level A required for unknown toxic chemicals; full-face SCBA mandatory; chemical-resistant suit with splash protection minimum
Level A required for unknown toxic chemicals; full-face SCBA mandatory; chemical-resistant suit with splash protection minimum
Isolation & Evacuation
ERG 123: Isolate spill/leak area immediately for at least 100m in all directions; initial evacuation 800m downwind if large spill
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 123).
First Actions for a UN 3502 Incident
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- 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.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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UN 3502 — Chemical under pressure, poisonous, n.o.HAZMAT RADIO NOTE — UN 3502
Product: Chemical under pressure, poisonous, n.o.s.
Class 2 / Non-Flammable Gas / ERG 123
PPE: Level A required for unknown toxic chemicals; full-face SCBA mandatory; chemical-resistant suit with splash protection minimum
ISOLATION: ERG 123: Isolate spill/leak area immediately for at least 100m in all directions; initial evacuation 800m downwind if large spill
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 3502 — Chemical under pressure, poisonous, n.o.s.
Class: 2 | Placard: Non-Flammable Gas | ERG Guide: 123
Appearance: Not otherwise specified (n.o.s.) entry covering various toxic chemicals under pressure. May be gas, liquefied gas, or dissolved gas. Physical characteristics vary by specific chemical.
Water Reactivity: Variable depending on specific chemical; may range from no reaction to violent reactivity
Extinguishing: Do not use water spray; use dry chemical, CO2, or inert gas as appropriate for specific chemical
PPE: Level A required for unknown toxic chemicals; full-face SCBA mandatory; chemical-resistant suit with splash protection minimum
Isolation: ERG 123: Isolate spill/leak area immediately for at least 100m in all directions; initial evacuation 800m downwind if large spill
— Key Hazards —
• TOXIC; may be fatal if inhaled or absorbed through skin.
• Vapors may be irritating and/or corrosive.
• Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
— First Actions —
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• 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.
SOURCE: allfirefighter.com/hazmat/un/chemical-under-pressure-poisonous-un-3502 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3502 Chemical under pressure, poisonous, n.o.s. Cls2 ERG123 | allfirefighter.com/hazmat/un/chemical-under-pressure-poisonous-un-3502SMS / 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/chemical-under-pressure-poisonous-un-3502
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Frequently Asked Questions about UN 3502
UN 3502 is Chemical under pressure, poisonous, n.o.s., assigned to ERG Guide 123.
ERG Guide 123 applies for initial isolation, protective actions and first response guidance.
Yes. Chemical under pressure, poisonous, n.o.s. can present a fire, combustion or vapor ignition hazard; keep it away from heat, sparks and flames.
Yes. Avoid skin, eye and respiratory contact; corrosive vapors or liquids can cause severe burns.
Yes. Inhalation, ingestion, skin absorption or contaminated runoff may create serious health hazards.
Pressurized containers may rupture, rocket or vent hazardous gas when heated or damaged.
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.