UN 2578 — Phosphorus trioxide
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Phosphorus trioxide is a corrosive phosphorus oxide that reacts with moisture. Responders should control dust, avoid water contact with product and monitor for acidic fumes.
Hazard overview: Moist air or water can convert the solid into acidic products with heat release, increasing respiratory and skin burn hazards. Fire can add toxic phosphorus oxide fumes and contaminated runoff.
Response guidance: Isolate the release, avoid raising dust and keep water streams off the product unless directed by specialist guidance. Use dry compatible materials for containment and rely on ERG 157, SDS and monitoring to set protective actions.
Firefighter training notes: Training should emphasize dry handling, acid-fume recognition and dust suppression without unsafe water application. Decon planning must account for corrosive residues.
Regulatory context: UN 2578 is listed as Phosphorus trioxide, Class 8 corrosive. Confirm exact product identity and packaging through shipping papers and SDS before cleanup.
Storage & handling: Store dry and sealed, away from water, bases, oxidizers and incompatible metals. Protect containers from humidity and heat.
UN 2578 Quick Details
Common Hazards of UN 2578
- Corrosive phosphorus oxide; dust or fumes can injure eyes, skin and the respiratory tract.
- Reacts with water or moist air to form acidic products and heat.
- Fuming or dust releases may create irritating, corrosive atmospheres in confined areas.
- Fire or decomposition may produce toxic phosphorus oxides.
- Water contact can increase heat, fuming and corrosive runoff.
- Containers may rupture when heated.
- Contaminated runoff can be acidic and harmful to waterways.
Chemical Identity & Physical Properties
Phosphorus trioxide is generally a white to yellowish crystalline solid or powder with an unpleasant odor. It can absorb moisture from air and fume under damp conditions.
| Also known as | Phosphorous trioxideDiphosphorus trioxideP2O3Phosphorus(III) oxideTetraphosphorus hexoxide |
| CAS Number | 1314-24-5 |
| Appearance | White to yellowish crystalline solid or powder. Garlic-like or unpleasant odor. Deliquescent, meaning it absorbs moisture from air. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | 173C (343F) sublimes |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts with water to form phosphorous acid (H3PO3), generating heat and toxic fumes |
Fireground Response Guidance — UN 2578
Extinguishing Media
PPE Requirements
SCBA is required for dust, fume or fire conditions. Chemical protective clothing, gloves and sealed eye/face protection should prevent contact with acidic material.
Isolation & Evacuation
First Actions for a UN 2578 Incident
- Call 911 and the emergency response number shown on shipping papers; confirm the material with ERG, SDS and container markings.
- Keep unauthorized personnel away and establish hot, warm and cold zones before entry.
- Stay upwind, uphill and upstream; avoid low areas where vapors, dust or runoff may collect.
- Avoid breathing vapors, dust, mist or decomposition products and prevent skin or eye contact.
- Do not touch damaged packages or containers unless properly trained and wearing suitable chemical PPE.
- Ventilate confined spaces only after atmospheric monitoring and only with trained, equipped personnel.
- Use ERG Guide 157, SDS, shipping papers and monitoring results for isolation, PPE and fire-control decisions.
📋 Copy & Share Field Card
UN 2578 — Phosphorus trioxideUse 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.