UN 1905 — Selenic acid
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1905 is Selenic acid, a toxic corrosive oxidizing acid assigned to ERG Guide 154. It can form corrosive selenate solutions and toxic selenium-containing contamination.
Hazard overview: UN 1905 presents acid burns, oxidizer reactivity, selenium toxicity, heat-on-dilution and contaminated-runoff hazards. Keep organics and reducing agents away.
Response guidance: For a UN 1905 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 154. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1905 should emphasize exposure routes, air monitoring, PPE selection, decontamination, runoff containment and ERG/SDS verification. Use ERG 154, SDS and local SOP.
Regulatory context: Selenic acid 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, concentration, 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: Selenic acid should be stored in compatible corrosion-resistant containers with secondary containment, away from incompatible chemicals, heat and unauthorized access. Follow SDS for oxidizers, acids, bases, solvents or toxic ingredients in the specific product.
UN 1905 Quick Details
Common Hazards of UN 1905
- TOXIC and CORROSIVE oxidizing acid; inhalation, ingestion or skin/eye contact may cause severe injury.
- Can cause severe burns and may create selenium-containing toxic contamination.
- Soluble in water with heat generation; runoff may contain corrosive selenate solution.
- Oxidizing acid may react with combustibles, organics or reducing agents.
- Heating or fire may produce selenium oxides and corrosive/toxic fumes.
- Contact with metals may release flammable hydrogen gas.
- Containers may rupture or fail when heated.
Chemical Identity & Physical Properties
Colorless to white crystalline solid or concentrated aqueous solution. Odorless. Hygroscopic and deliquescent.
| Also known as | Selenium acidSelenious acidHydrogen selenateSelenic(VI) acid |
| CAS Number | 7783-08-6 |
| Appearance | Colorless to white crystalline solid or concentrated aqueous solution. Odorless. Hygroscopic and deliquescent. |
| Flash Point | Not applicable (non-flammable oxidizing solid) |
| Boiling Point | 260C (500F) with decomposition |
| Vapor Density | Not applicable (solid/solution) |
| Water Reactivity | Soluble in water with heat generation; forms corrosive selenate solutions |
Fireground Response Guidance — UN 1905
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, mist, dust, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS for corrosive contact.
Isolation & Evacuation
First Actions for a UN 1905 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, fumes, dust, mist or spray and avoid skin or eye contact.
- Do not touch or walk through 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 leak area and expand the perimeter if vapor, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 154, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1905 — Selenic acidUse 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.