☣️ UN 1955 • CLASS 2
Compressed gas, poisonous, 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 1955
Class: 2
Placard type: Toxic Gas
ERG: Guide 123 (check current ERG)
Isolation: ERG 123: Isolate 800m (0.5 mi) all directions initially; evacuate 3.2 km (2 mi) downwind if large spill; protective action distance up to 11 km (7 mi) downwind for large spills during day
Chemical & Response Details
| Also known as | Toxic compressed gas n.o.s.Poisonous gas n.o.s.Compressed toxic gas Zone AHazardous compressed gas n.o.s. |
| Appearance | Compressed gas stored under pressure in cylinders or tanks. Physical state, color, and odor vary depending on specific gas; may be colorless or have distinct odor as warning agent. |
| Flash Point | Not applicable (compressed gas) |
| Boiling Point | Not applicable (varies by specific gas composition) |
| Vapor Density | Varies by composition; typically heavier than air for Zone A toxic gases |
| Water Reactivity | Varies by specific gas; some may react violently with water, others inert |
| Extinguishing | Do not use water; use appropriate gas-specific agent or allow to dissipate in well-ventilated area |
| PPE | ⚠️ Level A required for Zone A gases; fully encapsulating suit with SCBA; immediate evacuation if no specialized training |
| Isolation | ERG 123: Isolate 800m (0.5 mi) all directions initially; evacuate 3.2 km (2 mi) downwind if large spill; protective action distance up to 11 km (7 mi) downwind for large spills during day |
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.
- 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
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 1955 — Compressed gas, poisonous, n.o.s. (Inhal HAZMAT RADIO NOTE — UN 1955
Product: Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A)
Class 2 / Toxic Gas / ERG 123
PPE: Level A required for Zone A gases; fully encapsulating suit with SCBA; immediate evacuation if no specialized training
ISOLATION: ERG 123: Isolate 800m (0.5 mi) all directions initially; evacuate 3.2 km (2 mi) downwind if large spill; protective action distance up to 11 km (7 mi) downwind for large spills during day
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 1955 — Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A)
Class: 2 | Placard: Toxic Gas | ERG Guide: 123
Appearance: Compressed gas stored under pressure in cylinders or tanks. Physical state, color, and odor vary depending on specific gas; may be colorless or have distinct odor as warning agent.
Water Reactivity: Varies by specific gas; some may react violently with water, others inert
Extinguishing: Do not use water; use appropriate gas-specific agent or allow to dissipate in well-ventilated area
PPE: Level A required for Zone A gases; fully encapsulating suit with SCBA; immediate evacuation if no specialized training
Isolation: ERG 123: Isolate 800m (0.5 mi) all directions initially; evacuate 3.2 km (2 mi) downwind if large spill; protective action distance up to 11 km (7 mi) downwind for large spills during day
— 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 —
• 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/1955 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1955 Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A) Cls2 ERG123 | allfirefighter.com/hazmat/un/1955SMS / 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/1955
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FAQ
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
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; immediate evacuation if no specialized training
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 123 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.