UN 2471 — Osmium tetroxide
Placard: Toxic. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2471 is Osmium tetroxide, a highly toxic corrosive oxidizer assigned to ERG Guide 154. Vapors can severely injure eyes, lungs and skin.
Hazard overview: HIGHLY TOXIC and CORROSIVE oxidizing solid; vapor can severely injure eyes, lungs and skin. Vapor may be harmful at very low concentrations and can cause delayed eye or respiratory injury. May intensify fire involving combustibles and react with reducing agents or organics.
Response guidance: For UN 2471, isolate the area, avoid skin contact and use SCBA where vapor, dust, gas or fire is present. Control ignition or contamination hazards and contain runoff using SDS and ERG 154.
Firefighter training notes: Training for UN 2471 should emphasize exposure routes, SCBA use, vapor/dust monitoring, fire behavior, decontamination, runoff containment and SDS verification. Use ERG 154, SDS and local SOP.
Regulatory context: Osmium tetroxide 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: Osmium tetroxide should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 2471 Quick Details
Common Hazards of UN 2471
- HIGHLY TOXIC and CORROSIVE oxidizing solid; vapor can severely injure eyes, lungs and skin.
- Vapor may be harmful at very low concentrations and can cause delayed eye or respiratory injury.
- May intensify fire involving combustibles and react with reducing agents or organics.
- Contact can stain or damage skin and eyes; avoid all exposure.
- Heating may produce toxic osmium oxide fumes.
- Runoff and residues may carry toxic heavy-metal contamination.
- Use specialist hazmat controls for containment and decontamination.
Chemical Identity & Physical Properties
Pale yellow to yellow-green crystalline solid or colorless to pale yellow liquid (melts at 40°C). Pungent, chlorine-like acrid odor. Highly volatile even at room temperature.
| Also known as | Osmic acidOsmium(VIII) oxideOsmic anhydrideOsmium oxide |
| CAS Number | 20816-12-0 |
| Appearance | Pale yellow to yellow-green crystalline solid or colorless to pale yellow liquid (melts at 40°C). Pungent, chlorine-like acrid odor. Highly volatile even at room temperature. |
| Flash Point | Not applicable (non-flammable oxidizer) |
| Boiling Point | 130°C (266°F) |
| Vapor Density | 8.8 (much heavier than air) |
| Water Reactivity | Soluble in water; reacts slowly to form osmic acid solution. No violent reaction. |
Fireground Response Guidance — UN 2471
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and fully encapsulating chemical protective clothing for close entry or unknown concentrations. Protect against severe chemical, thermal and eye exposure.
Isolation & Evacuation
First Actions for a UN 2471 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 dust, liquid, 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 2471 — Osmium tetroxideUse 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.