☣️ UN 3305 • CLASS 2

UN 3305 — Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A)

Placard: Toxic Gas. ERG Guide 119. 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.

Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) is a Zone A toxic gas entry with severe inhalation hazard. Releases require immediate isolation, air monitoring and specialized hazmat control.

Hazard overview: Toxic flammable corrosive gas may be fatal if inhaled and may also be corrosive, oxidizing or flammable depending on the exact gas. Vapors can spread along the ground and threaten downwind areas.

Response guidance: Use ERG Guide 119 and Table 1 distances, stay upwind, deny entry and evacuate downwind as directed. Do not attempt leak control without Level A protection and gas-specific monitoring.

UN 3305 Quick Details

UN 3305

Product name: Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A)

DOT Class: 2

Placard type: Toxic Gas

ERG Guide: 119 (check current ERG)

Initial isolation: ERG 119: isolate spill or leak area immediately for at least 100m in all directions; if tank/rail car involved in fire, isolate 1600m in all directions and consider initial evacuation for 800m in all directions

Common Hazards of UN 3305

TOXIC; may be fatal if inhaled or absorbed through skin. Some may cause severe skin burns and.
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.
Flammable; may be ignited by heat, sparks or flames.
May form explosive mixtures with air. Ethylene oxide (UN1040) may react explosively even in the.
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.

Chemical Identity & Physical Properties

Compressed gas mixture under pressure; specific physical properties vary by composition. Contact with liquefied gas may cause frostbite due to extreme cold.

Also known as	Compressed poisonous flammable corrosive gas n.o.s.Toxic flammable corrosive compressed gasPoisonous compressed gas Zone A
Appearance	Compressed gas mixture under pressure; specific physical properties vary by composition. Contact with liquefied gas may cause frostbite due to extreme cold.
Flash Point	Not applicable (flammable compressed gas)
Boiling Point	Not applicable (varies by specific gas composition)
Vapor Density	Heavier than air (Zone A classification indicates high vapor density)
Water Reactivity	Corrosive properties may cause reaction with water; specific reactivity depends on gas composition

Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.

Fireground Response Guidance — UN 3305

Extinguishing Media

Do not use water or foam; use dry chemical or CO2 if appropriate for specific gas; allow fire to burn if safe to do so

PPE Requirements

⚠️ Level A required for Zone A gases; fully encapsulating suit with SCBA; avoid all contact with gas or liquid

Level A required for Zone A gases; fully encapsulating suit with SCBA; avoid all contact with gas or liquid.

Isolation & Evacuation

ERG 119: isolate spill or leak area immediately for at least 100m in all directions; if tank/rail car involved in fire, isolate 1600m in all directions and consider initial evacuation for 800m in all directions

Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 119).

First Actions for a UN 3305 Incident

CALL 911, then contact the emergency response telephone number shown on shipping papers, if available.
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.
For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
For non-highlighted materials, increase downwind protective distance based on conditions and incident command guidance.

📋 Copy & Share Field Card

UN 3305 — Compressed gas, poisonous, flammable, co

HAZMAT RADIO NOTE — UN 3305 Product: Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) Class 2 / Toxic Gas / ERG 119 PPE: Level A required for Zone A gases; fully encapsulating suit with SCBA; avoid all contact with gas or liquid ISOLATION: ERG 119: isolate spill or leak area immediately for at least 100m in all directions; if tank/rail car involved in fire, isolate 1600m in all directions and consider initial 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.

SMS WhatsApp

=== IC HAZMAT BRIEFING === UN 3305 — Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) Class: 2 | Placard: Toxic Gas | ERG Guide: 119 Appearance: Compressed gas mixture under pressure; specific physical properties vary by composition. Contact with liquefied gas may cause frostbite due to extreme cold. Water Reactivity: Corrosive properties may cause reaction with water; specific reactivity depends on gas composition Extinguishing: Do not use water or foam; use dry chemical or CO2 if appropriate for specific gas; allow fire to burn if safe to do so PPE: Level A required for Zone A gases; fully encapsulating suit with SCBA; avoid all contact with gas or liquid Isolation: ERG 119: isolate spill or leak area immediately for at least 100m in all directions; if tank/rail car involved in fire, isolate 1600m in all directions and consider initial evacuation for 800m in all directions — Key Hazards — • TOXIC; may be fatal if inhaled or absorbed through skin. Some may cause severe skin burns and. • Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. • Fire will produce irritating, corrosive and/or toxic gases. — First Actions — • CALL 911, then contact the emergency response telephone number shown on shipping papers, if available. • 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/compressed-gas-poisonous-flammable-un-3305 | Always use current ERG + SOP/SOGIC BRIEFING

Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.

SMS (short)

UN3305 Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) Cls2 ERG119 | allfirefighter.com/hazmat/un/compressed-gas-poisonous-flammable-un-3305SMS / 160 CHAR

Use for: Quick text to command or incoming units. Fits in a single SMS.

Open in Messages WhatsApp

⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/compressed-gas-poisonous-flammable-un-3305

Related UN Numbers in Class 2

Open Class Guide →Hazmat Hub →

UN 1001 UN 1002 UN 1003 UN 1005 UN 1006 UN 1008 UN 1009 UN 1011 UN 1012 UN 1013 UN 1016 UN 1017

Discovery block for training / quick reference. Always consult the current ERG + your SOP/SOG for operations.

Frequently Asked Questions about UN 3305

UN 3305 is Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A), assigned to ERG Guide 119 and placarded as Toxic Gas.

Yes. Toxic flammable corrosive gas presents a serious toxic exposure hazard; avoid inhalation, ingestion, skin contact and contaminated runoff.

Yes, corrosive effects are possible. Avoid skin and eye contact and use chemical-resistant protection.

Yes or potentially so under incident conditions. Remove ignition sources and control vapors from a safe distance.

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.