☣️ UN 3305 • CLASS 2
Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A)
Placard: Toxic 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 3305
Class: 2
Placard type: Toxic Gas
ERG: Guide 119 (check current ERG)
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
Chemical & Response Details
| 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 |
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
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.
- 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 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.
=== 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 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/3305 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3305 Compressed gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) Cls2 ERG119 | allfirefighter.com/hazmat/un/3305SMS / 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/3305
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FAQ
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.
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 A required for Zone A gases; fully encapsulating suit with SCBA; avoid all contact with gas or liquid
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 119 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.