UN 2657 — Selenium disulphide
Placard: Toxic. ERG Guide 153. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2657 is Selenium disulphide, a toxic selenium compound assigned to ERG Guide 153. Dust, product form and selenium runoff are key concerns.
Hazard overview: TOXIC selenium compound; inhalation of dust or skin/eye contact may cause injury. Combustible dust/solid behavior depends on particle size and formulation; avoid dust clouds. Heating or fire may produce toxic selenium and sulfur oxide fumes.
Response guidance: For UN 2657, isolate the area, avoid skin contact and use SCBA where dust, vapor, mist or fire is present. Prevent spread of contaminated runoff, cool containers from protection and verify controls with SDS and ERG 153.
Firefighter training notes: Training for UN 2657 should emphasize toxic exposure routes, skin absorption, SCBA use, dust/vapor control, decontamination, runoff containment and SDS verification. Use ERG 153, SDS and local SOP.
Regulatory context: Selenium disulphide is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Selenium disulphide should be stored in tightly closed labeled containers in a secure toxic-material area with dust control, secondary containment, restricted access and SDS-based segregation.
UN 2657 Quick Details
Common Hazards of UN 2657
- TOXIC selenium compound; inhalation of dust or skin/eye contact may cause injury.
- Combustible dust/solid behavior depends on particle size and formulation; avoid dust clouds.
- Heating or fire may produce toxic selenium and sulfur oxide fumes.
- Dust can contaminate clothing, tools and runoff.
- Runoff may carry toxic selenium contamination and harm waterways.
- Containers may fail when heated.
- Exact product form and concentration should be verified from SDS.
Chemical Identity & Physical Properties
Bright orange to red-orange powder or crystalline solid. Odorless or slight odor. Insoluble in water.
| Also known as | Selenium sulfideDiselenium disulfideSelenium(IV) sulfideSelsun |
| CAS Number | 7488-56-4 |
| Appearance | Bright orange to red-orange powder or crystalline solid. Odorless or slight odor. Insoluble in water. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | Not applicable (decomposes above 100°C) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | No significant reaction with water; insoluble |
Fireground Response Guidance — UN 2657
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for dust, vapor, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing.
Isolation & Evacuation
First Actions for a UN 2657 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, 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 dust, liquid, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 153, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2657 — Selenium disulphideUse 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.