UN 2318 — Sodium hydrosulphide, with less than 25% water of crystallization
Placard: Spontaneously Combustible. ERG Guide 135. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2318 is Sodium hydrosulphide, with less than 25% water of crystallization, a spontaneously combustible moisture-reactive sulfide assigned to ERG Guide 135. Moisture can release toxic and flammable hydrogen sulfide gas.
Hazard overview: SPONTANEOUSLY COMBUSTIBLE and moisture-reactive sodium hydrosulphide; may ignite on contact with moist air. Reacts with water or moisture, releasing toxic and flammable hydrogen sulfide gas. Hydrogen sulfide is heavier than air and may collect in low or confined areas.
Response guidance: For a UN 2318 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 135. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff, dust or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2318 should emphasize moisture-triggered H2S release, spontaneous ignition, no-water/no-foam tactics, gas monitoring, evacuation and dry-agent control. Use ERG 135, SDS and local SOP.
Regulatory context: Sodium hydrosulphide, with less than 25% water of crystallization is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting, waste handling and environmental requirements 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: Sodium hydrosulphide, with less than 25% water of crystallization should be stored dry in sealed compatible containers away from moisture, acids, oxidizers, ignition sources and confined low areas. Provide H2S monitoring where appropriate and keep compatible dry media available.
UN 2318 Quick Details
Common Hazards of UN 2318
- SPONTANEOUSLY COMBUSTIBLE and moisture-reactive sodium hydrosulphide; may ignite on contact with moist air.
- Reacts with water or moisture, releasing toxic and flammable hydrogen sulfide gas.
- Hydrogen sulfide is heavier than air and may collect in low or confined areas.
- Water, foam or CO2 may worsen reaction or spread toxic gas.
- May re-ignite after apparent extinguishment.
- Fire may produce sulfur oxides and toxic/corrosive gases.
- Runoff may create fire, toxic gas and environmental hazards.
Chemical Identity & Physical Properties
Yellow to brick-red crystalline solid or flakes with a strong hydrogen sulfide (rotten egg) odor. Highly hygroscopic and deliquescent.
| Also known as | Sodium hydrogen sulfideSodium bisulfideSodium sulfhydrateNaHS |
| CAS Number | 16721-80-5 |
| Appearance | Yellow to brick-red crystalline solid or flakes with a strong hydrogen sulfide (rotten egg) odor. Highly hygroscopic and deliquescent. |
| Flash Point | Not applicable (pyrophoric solid, ignites spontaneously on contact with moist air) |
| Boiling Point | Not applicable (decomposes at approximately 350C/662F) |
| Vapor Density | Not applicable (solid, but releases H2S gas which is 1.2 times heavier than air) |
| Water Reactivity | Reacts with water releasing toxic and flammable hydrogen sulfide gas; exothermic reaction |
Fireground Response Guidance — UN 2318
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical protective clothing for dust, fire, spill or hydrogen sulfide risk. Level A may be needed for large spills, confined spaces or unknown vapor levels.
Isolation & Evacuation
First Actions for a UN 2318 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 breathing vapors, dust, mist, smoke or fumes and avoid skin or eye contact.
- Keep water, foam, CO2 and moisture away from released material unless specialist guidance confirms compatibility.
- Do not touch damaged containers or spilled 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 spill or release area and expand the perimeter for fire involvement, vapor spread, dust generation, water reaction or unknown product identity.
- Use ERG Guide 135, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2318 — Sodium hydrosulphide, with less than 25%Use 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.