UN 1402 — Calcium carbide
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1402 is Calcium carbide, a dangerous-when-wet Class 4 material assigned to ERG Guide 138. Contact with water or moisture can release flammable acetylene gas, creating fire, toxic exposure or pressure hazards.
Hazard overview: UN 1402 presents water-reactive, ignition and reaction-gas hazards. Moisture can generate flammable acetylene gas and heat, so responders should keep the material dry, control runoff and use only compatible dry agents under incident command.
Response guidance: For a UN 1402 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 138. Establish incident command, isolate the area, stay upwind, avoid unnecessary disturbance of powder, piles or damaged packaging, and use only extinguishing agents compatible with the specific material.
Firefighter training notes: Training for UN 1402 should emphasize dangerous-when-wet behavior, reaction gas identification, dry-agent selection and downwind gas control. Common errors include using water or foam directly, entering low areas without monitoring and underestimating re-ignition. Use ERG 138, SDS and hazmat SOP.
Regulatory context: Calcium carbide is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Calcium carbide should be stored in tightly closed compatible containers in a cool, dry, well-ventilated area away from water, moisture, acids, oxidizers, heat and ignition sources. Protect containers from damage and keep compatible dry spill-control media available where required.
UN 1402 Quick Details
Common Hazards of UN 1402
- DANGEROUS WHEN WET; contact with water or moisture can release flammable acetylene gas.
- May ignite on contact with water or moist air.
- Reaction with water may generate heat and pressure.
- May be ignited by heat, sparks or flames and may re-ignite after apparent extinguishment.
- Containers may rupture or explode when heated.
- Runoff or water application may spread contamination and increase gas generation.
- Avoid low, enclosed or poorly ventilated areas where reaction gases may accumulate.
Chemical Identity & Physical Properties
Grayish-black or brown crystalline solid with a garlic-like odor when pure. Commercial grades appear as irregular hard lumps.
| Also known as | Calcium acetylideCalcium dicarbideAcetylenogenCarbide |
| CAS Number | 75-20-7 |
| Appearance | Grayish-black or brown crystalline solid with a garlic-like odor when pure. Commercial grades appear as irregular hard lumps. |
| Flash Point | Not applicable (reacts with water to produce flammable acetylene gas) |
| Boiling Point | Not applicable (decomposes above 2300C/4172F) |
| Vapor Density | Not applicable (solid, but produces acetylene gas with vapor density 0.9) |
| Water Reactivity | Reacts vigorously with water producing flammable acetylene gas and heat; may ignite spontaneously |
Fireground Response Guidance — UN 1402
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for any suspected flammable acetylene gas, fire, vapor or confined-space exposure. Chemical-resistant clothing, gloves and eye/face protection should be selected from SDS and incident command; air monitoring is important.
Isolation & Evacuation
First Actions for a UN 1402 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.
- Avoid low areas where flammable acetylene gas may collect.
- Do not touch spilled material or damaged containers unless properly trained and equipped.
- Keep water, foam and moisture away from the released material unless incident command confirms a compatible cooling or control use.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if water contact, fire or gas generation is suspected.
- Use ERG Guide 138, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1402 — Calcium carbideUse 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.