UN 2949 — Sodium hydrosulphide, hydrated, with not less than 25% water of crystallization
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2949 is Sodium hydrosulphide, hydrated, with not less than 25% water of crystallization, a corrosive sulfide solid assigned to ERG Guide 154. Hydrogen sulfide release and acid incompatibility are critical.
Hazard overview: CORROSIVE sulfide solid; dust or solution can burn eyes, skin and respiratory tissue. May release highly toxic hydrogen sulfide gas, especially with acids, heat or poor ventilation. Hydrogen sulfide is heavier than air and may collect in low or confined areas.
Response guidance: For UN 2949, isolate the area, avoid skin contact and use SCBA where dust, vapor, mist or fire is present. Contain runoff and verify controls with SDS and ERG 154.
Firefighter training notes: Training for UN 2949 should emphasize exposure routes, SCBA use, vapor/dust monitoring, decontamination, runoff containment and SDS verification. Use ERG 154, SDS and local SOP.
Regulatory context: Sodium hydrosulphide, hydrated, with not less than 25% water of crystallization is regulated as a hazardous material for transport and emergency response. Storage, reporting, exposure, waste and incident-notification duties depend on quantity, formulation and jurisdiction; verify shipping papers, SDS and authority guidance.
Storage & handling: Sodium hydrosulphide, hydrated, with not less than 25% water of crystallization should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 2949 Quick Details
Common Hazards of UN 2949
- CORROSIVE sulfide solid; dust or solution can burn eyes, skin and respiratory tissue.
- May release highly toxic hydrogen sulfide gas, especially with acids, heat or poor ventilation.
- Hydrogen sulfide is heavier than air and may collect in low or confined areas.
- Non-flammable solid, but released H2S is flammable and toxic.
- Fire may produce sulfur oxides, hydrogen sulfide and corrosive/toxic smoke.
- Runoff may be alkaline/sulfide-contaminated and harmful to waterways.
- Odor is not a reliable warning for hydrogen sulfide exposure.
Chemical Identity & Physical Properties
Yellow to orange crystalline solid or flakes with a strong rotten egg (hydrogen sulfide) odor. Deliquescent, absorbs moisture from air.
| Also known as | Sodium hydrogen sulfide hydrateSodium bisulfide hydrateSodium sulfhydrate hydrateNaHS hydrate |
| CAS Number | 16721-80-5 |
| Appearance | Yellow to orange crystalline solid or flakes with a strong rotten egg (hydrogen sulfide) odor. Deliquescent, absorbs moisture from air. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid, but releases H2S gas which is heavier than air) |
| Water Reactivity | Dissolves readily releasing heat and toxic hydrogen sulfide gas (H2S). Keep wet to minimize H2S evolution but contact with water is hazardous. |
Fireground Response Guidance — UN 2949
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical-resistant protective clothing. Level A may be needed for heavy vapor, fuming, splash risk or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 2949 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Avoid breathing vapor, dust, gas, mist, smoke or fumes and avoid skin or eye contact.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Prevent contaminated liquid, dust, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 154, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2949 — Sodium hydrosulphide, hydrated, with notUse 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.