UN 2834 — Phosphorous acid
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2834 At a Glance
UN 2834 (Phosphorous acid) is listed as DOT Class 8 Corrosive and is assigned to ERG Guide 154. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.
UN 2834 is Phosphorous acid, a corrosive acidic solid assigned to ERG Guide 154. Dust, heat on dissolution and acidic runoff require control.
Hazard overview: CORROSIVE acidic solid; dust or solution can burn eyes, skin and respiratory tissue. Dissolves in water with heat release, forming acidic solution. Non-combustible, but heating can produce phosphorus oxides and irritating acidic fumes.
Response guidance: For UN 2834, isolate the area, avoid skin contact and use SCBA where dust, vapor, mist or fire is present. Contain corrosive/toxic runoff and verify controls with SDS and ERG 154.
Firefighter training notes: Training for UN 2834 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: Phosphorous acid 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: Phosphorous acid should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 2834 Quick Details
Common Hazards of UN 2834
- CORROSIVE acidic solid; dust or solution can burn eyes, skin and respiratory tissue.
- Dissolves in water with heat release, forming acidic solution.
- Non-combustible, but heating can produce phosphorus oxides and irritating acidic fumes.
- Contact with metals may generate flammable hydrogen gas under acidic conditions.
- Runoff may be acidic, corrosive and harmful to waterways.
- Dust can irritate lungs and contaminate clothing or tools.
- Containers may fail when heated or exposed to moisture.
Chemical Identity & Physical Properties
White or yellowish crystalline solid or powder. Odorless or slight garlic-like odor. Hygroscopic, absorbs moisture from air.
| Also known as | Phosphonic acidOrthophosphorous acidTrihydroxyphosphine oxide |
| CAS Number | 10294-56-1 |
| Appearance | White or yellowish crystalline solid or powder. Odorless or slight garlic-like odor. Hygroscopic, absorbs moisture from air. |
| Flash Point | Not applicable (non-combustible solid) |
| Boiling Point | Decomposes at 200C (392F) before boiling |
| Vapor Density | Not applicable (solid at room temperature) |
| Water Reactivity | Dissolves in water releasing heat; forms acidic solution; no violent reaction |
Fireground Response Guidance — UN 2834
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, dust, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing.
Isolation & Evacuation
First Actions for a UN 2834 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 liquid, dust, 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 2834 — Phosphorous 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.