UN 2655 — Potassium fluorosilicate
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2655 is Potassium fluorosilicate, a toxic fluoride/silicate salt assigned to ERG Guide 151. Dust and fluoride-contaminated runoff are key hazards.
Hazard overview: TOXIC fluoride/silicate salt; inhalation of dust, ingestion or skin contact may cause severe injury. Dust can irritate or burn eyes, skin and respiratory tissue. Non-combustible solid, but heating can release toxic/corrosive fluoride fumes.
Response guidance: For UN 2655, 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 151.
Firefighter training notes: Training for UN 2655 should emphasize toxic exposure routes, skin absorption, SCBA use, dust/vapor control, decontamination, runoff containment and SDS verification. Use ERG 151, SDS and local SOP.
Regulatory context: Potassium fluorosilicate 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: Potassium fluorosilicate 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 2655 Quick Details
Common Hazards of UN 2655
- TOXIC fluoride/silicate salt; inhalation of dust, ingestion or skin contact may cause severe injury.
- Dust can irritate or burn eyes, skin and respiratory tissue.
- Non-combustible solid, but heating can release toxic/corrosive fluoride fumes.
- Slight solubility or acid contact can form acidic fluoride-containing solution.
- Runoff may be fluoride-contaminated and harmful to waterways.
- Avoid dust generation and secondary contamination of PPE or tools.
- Containers may fail when heated.
Chemical Identity & Physical Properties
White to colorless crystalline powder or granular solid. Odorless. Insoluble in water but slightly soluble in dilute acids.
| Also known as | Potassium hexafluorosilicatePotassium silicofluorideDipotassium hexafluorosilicatePSF |
| CAS Number | 16871-90-2 |
| Appearance | White to colorless crystalline powder or granular solid. Odorless. Insoluble in water but slightly soluble in dilute acids. |
| Flash Point | Not applicable (non-combustible inorganic salt) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid with negligible vapor pressure) |
| Water Reactivity | No significant reaction with water, but slightly soluble forming acidic solution |
Fireground Response Guidance — UN 2655
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 2655 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 151, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2655 — Potassium fluorosilicateUse 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.