UN 1955 — Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A)
Placard: Toxic Gas. ERG Guide 123. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1955 is Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A), a toxic inhalation hazard Zone A compressed gas entry assigned to ERG Guide 123. Exact gas identity controls the medical, corrosive and evacuation decisions.
Hazard overview: UN 1955 presents fatal inhalation, toxic/corrosive vapor, frostbite/contact and cylinder rupture hazards.
Response guidance: For a UN 1955 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 123. Establish incident command, isolate the area, stay upwind, control ignition or downwind hazards, cool exposed containers from a protected distance when appropriate and base entry decisions on monitoring and local SOP.
Firefighter training notes: Training for UN 1955 should emphasize toxic inhalation hazard procedures, ERG Table 1 use, gas monitoring, Level A entry decisions, cylinder control, evacuation and decontamination. Use ERG 123, SDS and local SOP.
Regulatory context: Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A) is regulated as a hazardous material for transportation and emergency response purposes. Requirements for storage, workplace exposure, emergency planning, spill reporting and waste handling vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Compressed gas, poisonous, n.o.s. (Inhalation Hazard Zone A) should be stored in a secure, ventilated toxic-gas area with restricted access, leak detection/monitoring where required, compatible cylinder restraints and emergency response planning according to SDS and local code.
UN 1955 Quick Details
Common Hazards of UN 1955
- TOXIC INHALATION HAZARD Zone A compressed gas; inhalation may be fatal.
- Vapors may be irritating, corrosive or otherwise toxic depending on the specific gas.
- Gas or liquefied gas contact may cause burns, severe injury and/or frostbite.
- Heavy gas may collect in low or confined areas.
- Cylinders exposed to fire may vent toxic/corrosive gas, rupture or rocket.
- Fire may produce irritating, corrosive and/or toxic gases.
- Specific protective-action distances must be confirmed from ERG Table 1, shipping papers and SDS.
Chemical Identity & Physical Properties
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.
| 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 |
Fireground Response Guidance — UN 1955
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and fully encapsulating chemical protective clothing for close entry or unknown concentrations. Level A may be needed; avoid all skin contact and follow toxic inhalation hazard procedures.
Isolation & Evacuation
First Actions for a UN 1955 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Treat the incident as a serious inhalation hazard; use Table 1/protective-action guidance where applicable.
- Avoid breathing gas, vapor, smoke or mist and avoid skin or eye contact.
- Do not touch damaged containers or spilled/released material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the release area and expand the perimeter for fire involvement, cylinder heating, vapor accumulation, unknown gas identity or downwind exposure.
- Use ERG Guide 123, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1955 — Compressed gas, poisonous, n.o.s. (InhalUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.