☣️ UN 3304 • CLASS 2
UN 3304 — Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A)
Placard: Toxic Gas. ERG Guide 125. 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, 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 corrosive compressed 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 125 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.
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UN 3304 Quick Details
UN 3304
Product name: Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A)
DOT Class: 2
Placard type: Toxic Gas
ERG Guide: 125 (check current ERG)
Initial isolation: ERG 125: Initial isolation 150m in all directions; protective action distance 1.4km+ downwind daytime, 3.4km+ downwind nighttime for large spills
Common Hazards of UN 3304
- TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin.
- Vapors are extremely irritating and 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.
- Some of these materials may react violently with water.
Chemical Identity & Physical Properties
Varies by specific substance; typically colorless to pale colored gas under pressure. May have pungent, irritating, or acrid odor. Liquefies under pressure in cylinders.
| Also known as | Compressed poisonous corrosive gas n.o.s.Toxic corrosive gas under pressurePoisonous compressed gas corrosive n.o.s.Inhalation hazard Zone A compressed gas |
| Appearance | Varies by specific substance; typically colorless to pale colored gas under pressure. May have pungent, irritating, or acrid odor. Liquefies under pressure in cylinders. |
| Flash Point | Not applicable (non-flammable compressed gas) |
| Boiling Point | Not applicable (varies by specific gas composition) |
| Vapor Density | Heavier than air (varies by specific gas, most toxic corrosive gases are denser than air) |
| Water Reactivity | May react with water producing corrosive and/or toxic fumes; reaction severity varies by specific gas |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3304
Extinguishing Media
Not applicable for gas leak; water spray may be used to absorb vapors from distance but avoid direct contact
PPE Requirements
⚠️ Level A required for Zone A materials; fully encapsulating chemical protective suit with SCBA; extreme inhalation hazard
Level A required for Zone A materials; fully encapsulating chemical protective suit with SCBA; extreme inhalation hazard.
Isolation & Evacuation
ERG 125: Initial isolation 150m in all directions; protective action distance 1.4km+ downwind daytime, 3.4km+ downwind nighttime for large spills
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 125).
First Actions for a UN 3304 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.
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UN 3304 — Compressed gas, poisonous, corrosive, n.HAZMAT RADIO NOTE — UN 3304
Product: Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A)
Class 2 / Toxic Gas / ERG 125
PPE: Level A required for Zone A materials; fully encapsulating chemical protective suit with SCBA; extreme inhalation hazard
ISOLATION: ERG 125: Initial isolation 150m in all directions; protective action distance 1.4km+ downwind daytime, 3.4km+ downwind nighttime for large spills
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 3304 — Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A)
Class: 2 | Placard: Toxic Gas | ERG Guide: 125
Appearance: Varies by specific substance; typically colorless to pale colored gas under pressure. May have pungent, irritating, or acrid odor. Liquefies under pressure in cylinders.
Water Reactivity: May react with water producing corrosive and/or toxic fumes; reaction severity varies by specific gas
Extinguishing: Not applicable for gas leak; water spray may be used to absorb vapors from distance but avoid direct contact
PPE: Level A required for Zone A materials; fully encapsulating chemical protective suit with SCBA; extreme inhalation hazard
Isolation: ERG 125: Initial isolation 150m in all directions; protective action distance 1.4km+ downwind daytime, 3.4km+ downwind nighttime for large spills
— Key Hazards —
• TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin.
• Vapors are extremely irritating and corrosive.
• Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
— 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-corrosive-un-3304 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3304 Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A) Cls2 ERG125 | allfirefighter.com/hazmat/un/compressed-gas-poisonous-corrosive-un-3304SMS / 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/compressed-gas-poisonous-corrosive-un-3304
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Frequently Asked Questions about UN 3304
UN 3304 is Compressed gas, poisonous, corrosive, n.o.s. (Inhalation Hazard Zone A), assigned to ERG Guide 125 and placarded as Toxic Gas.
Yes. Toxic corrosive compressed 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.
Gas can spread downwind, collect in low or confined areas, displace oxygen or create toxic exposure depending on the material.
Use caution. May react with water producing corrosive and/or toxic fumes; reaction severity varies by specific gas
Not applicable for gas leak; water spray may be used to absorb vapors from distance but avoid direct contact.
Level A required for Zone A materials; fully encapsulating chemical protective suit with SCBA; extreme inhalation hazard.
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.