UN 1017 — Chlorine
Placard: Toxic Gas. ERG Guide 124. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1017 is Chlorine, a Class 2 toxic gas assigned to ERG Guide 124. It is a greenish-yellow, corrosive oxidizing gas that can be fatal by inhalation and can collect in low areas.
Hazard overview: UN 1017 presents toxic inhalation, corrosive contact and oxidizer hazards. Chlorine can damage the respiratory tract, eyes and skin, form acidic solutions with water and support combustion even though it is not itself flammable.
Response guidance: For a UN 1017 incident, responders should confirm the product using shipping papers, cylinder markings, SDS and ERG Guide 124. Establish incident command, isolate the area, stay upwind, avoid vapor contact, use air monitoring when available and consult ERG Table 1 when applicable.
Firefighter training notes: Training for UN 1017 should emphasize toxic inhalation risk, corrosive vapor exposure, SCBA discipline, Table 1 protective actions and cylinder leak control limitations. Common errors include relying on odor, entering low areas without monitoring, applying water to a reactive leak and selecting splash PPE without respiratory protection.
Regulatory context: Chlorine is regulated as a Class 2 hazardous material for transportation and emergency response purposes. Cylinder, workplace exposure, storage, reporting and environmental requirements may vary by product, quantity and jurisdiction. Responders should verify current requirements through shipping papers, SDS, cylinder markings, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Chlorine cylinders should be stored secured in a cool, dry, well-ventilated area with appropriate toxic gas controls, leak detection where required and segregation from incompatible materials. Protect cylinders from heat, corrosion, impact, valve damage and unauthorized access.
UN 1017 Quick Details
Common Hazards of UN 1017
- TOXIC and/or CORROSIVE; may be fatal if inhaled.
- Gas or vapor may severely irritate or burn eyes, skin and respiratory tissue.
- Contact with liquefied gas may cause frostbite and chemical injury.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or vapor suppression may be corrosive or environmentally hazardous.
- Vapors may be heavier than air and collect in low or confined areas.
- Containers may rupture or rocket when heated.
- Chlorine does not burn but can support combustion and react with many materials.
- Water contact may create acidic, corrosive solutions.
Chemical Identity & Physical Properties
Greenish-yellow gas with a pungent, irritating odor detectable at very low concentrations. Shipped as a liquefied compressed gas.
| Also known as | Molecular chlorineCl2BertholiteDichlorine |
| CAS Number | 7782-50-5 |
| Appearance | Greenish-yellow gas with a pungent, irritating odor detectable at very low concentrations. Shipped as a liquefied compressed gas. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | -34C (-29F) |
| Vapor Density | 2.5 (heavier than air) |
| Water Reactivity | Reacts with water to form hypochlorous and hydrochloric acids; corrosive solution |
Fireground Response Guidance — UN 1017
Extinguishing Media
PPE Requirements
Positive-pressure SCBA is required for suspected toxic gas exposure. Chemical-protective clothing should be selected using SDS, monitoring results, leak conditions and incident command; Level A may be needed for close entry into unknown or high-concentration toxic/corrosive vapor.
Isolation & Evacuation
First Actions for a UN 1017 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.
- Do not touch damaged cylinders, tanks, valves or released material unless properly trained and equipped.
- Avoid breathing gas, vapor, mist or fire gases.
- Many toxic or liquefied gases may spread along the ground and collect in low or confined areas.
- Ventilate closed spaces before entering, but only if properly trained, equipped and authorized by incident command.
- Isolate the spill or leak area for at least 100 meters (330 feet) in all directions.
- For highlighted materials, consult ERG Table 1 for Initial Isolation and Protective Action Distances.
- For non-highlighted materials, increase the precautionary distance downwind based on release size, weather, monitoring and incident command.
📋 Copy & Share Field Card
UN 1017 — ChlorineUse 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.