☣️ UN 3309 • CLASS 2
UN 3309 — Liquefied 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.
UN 3309 covers a liquefied gas that is poisonous, flammable, corrosive, and assigned to Inhalation Hazard Zone A. Because the exact gas is not otherwise specified, responders should confirm shipping papers and SDS details before committing crews.
Hazard overview: This material may be fatal if inhaled and can cause corrosive injury or frostbite from gas or liquefied gas contact. Vapors may travel low to the ground, form explosive mixtures with air, and create severe downwind exposure risk.
Response guidance: Isolate the area, stay upwind and uphill, deny entry, and request hazmat support. Use dry chemical, CO2, or inert gas for fire control when appropriate; water spray should be limited to cooling containers from a distance.
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UN 3309 Quick Details
UN 3309
Product name: Liquefied 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: Initial isolation 800m (½ mile) all directions; protective action distance 3.2km (2 miles) downwind for large spills; 7.0km (4.3 miles) downwind if tank/rail car involved in fire
Common Hazards of UN 3309
- 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
Liquefied gas under pressure, appearance varies by specific composition. Contact with liquid causes severe frostbite; gas may be colorless or have varying colors depending on components.
| Also known as | Liquefied poisonous gas n.o.s.Toxic liquefied gas n.o.s.Compressed poisonous gas flammable corrosiveLiquefied toxic gas Zone A |
| Appearance | Liquefied gas under pressure, appearance varies by specific composition. Contact with liquid causes severe frostbite; gas may be colorless or have varying colors depending on components. |
| Flash Point | Not applicable (liquefied flammable gas under pressure) |
| Boiling Point | Varies by composition; typically below -40C (-40F) for Zone A materials |
| Vapor Density | Heavier than air (specific gravity > 1.0); vapors accumulate in low areas |
| Water Reactivity | May react with water producing toxic/corrosive gases; reaction severity depends on specific components |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3309
Extinguishing Media
Dry chemical, CO2, or inert gas; water spray only for cooling containers from distance
PPE Requirements
⚠️ Level A required: fully encapsulating chemical protective suit with SCBA; Zone A indicates extreme inhalation hazard
Level A required: fully encapsulating chemical protective suit with SCBA; Zone A indicates extreme inhalation hazard
Isolation & Evacuation
ERG 119: Initial isolation 800m (½ mile) all directions; protective action distance 3.2km (2 miles) downwind for large spills; 7.0km (4.3 miles) downwind if tank/rail car involved in fire
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 119).
First Actions for a UN 3309 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 3309 — Liquefied gas, poisonous, flammable, corHAZMAT RADIO NOTE — UN 3309
Product: Liquefied gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A)
Class 2 / Toxic Gas / ERG 119
PPE: Level A required: fully encapsulating chemical protective suit with SCBA; Zone A indicates extreme inhalation hazard
ISOLATION: ERG 119: Initial isolation 800m (½ mile) all directions; protective action distance 3.2km (2 miles) downwind for large spills; 7.0km (4.3 miles) downwind if tank/rail car involved in fire
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 3309 — Liquefied gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A)
Class: 2 | Placard: Toxic Gas | ERG Guide: 119
Appearance: Liquefied gas under pressure, appearance varies by specific composition. Contact with liquid causes severe frostbite; gas may be colorless or have varying colors depending on components.
Water Reactivity: May react with water producing toxic/corrosive gases; reaction severity depends on specific components
Extinguishing: Dry chemical, CO2, or inert gas; water spray only for cooling containers from distance
PPE: Level A required: fully encapsulating chemical protective suit with SCBA; Zone A indicates extreme inhalation hazard
Isolation: ERG 119: Initial isolation 800m (½ mile) all directions; protective action distance 3.2km (2 miles) downwind for large spills; 7.0km (4.3 miles) downwind if tank/rail car involved in fire
— 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 —
• 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/liquefied-gas-poisonous-flammable-un-3309 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3309 Liquefied gas, poisonous, flammable, corrosive, n.o.s. (Inhalation Hazard Zone A) Cls2 ERG119 | allfirefighter.com/hazmat/un/liquefied-gas-poisonous-flammable-un-3309SMS / 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/liquefied-gas-poisonous-flammable-un-3309
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Frequently Asked Questions about UN 3309
Yes. UN 3309 includes a flammable liquefied toxic gas that may ignite from heat, sparks, or flames.
It is listed as Inhalation Hazard Zone A, meaning a release can create an extreme toxic vapor hazard.
Level A fully encapsulating chemical protective clothing with SCBA is required for release response.
Use water spray only to cool containers from a distance; do not apply water directly unless the specific gas is confirmed compatible.
Shipping papers, placards, container markings, and SDS information should be used to identify the exact gas.
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.