☣️ UN 2834 • CLASS 8
UN 2834 — Phosphorous acid
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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UN 2834 Quick Details
UN 2834
Product name: Phosphorous acid
DOT Class: 8
Placard type: Corrosive
ERG Guide: 154 (check current ERG)
Initial isolation: ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
Common Hazards of UN 2834
- TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
- Contact with molten substance may cause severe burns to skin and eyes.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.).
- Corrosives in contact with metals may evolve flammable hydrogen gas.
Chemical Identity & Physical Properties
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2834
Extinguishing Media
Dry chemical, soda ash, lime; water spray may be used to dilute spills
PPE Requirements
⚠️ Level B minimum for spill response; chemical-resistant suit, gloves, boots; SCBA required for enclosed spaces or dust exposure
Isolation & Evacuation
ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 154).
First Actions for a UN 2834 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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📋 Copy & Share Field Card
UN 2834 — Phosphorous acidHAZMAT RADIO NOTE — UN 2834
Product: Phosphorous acid
Class 8 / Corrosive / ERG 154
PPE: Level B minimum for spill response; chemical-resistant suit, gloves, boots; SCBA required for enclosed spaces or dust exposure
ISOLATION: ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 2834 — Phosphorous acid
Class: 8 | Placard: Corrosive | ERG Guide: 154
Appearance: White or yellowish crystalline solid or powder. Odorless or slight garlic-like odor. Hygroscopic, absorbs moisture from air.
Water Reactivity: Dissolves in water releasing heat; forms acidic solution; no violent reaction
Extinguishing: Dry chemical, soda ash, lime; water spray may be used to dilute spills
PPE: Level B minimum for spill response; chemical-resistant suit, gloves, boots; SCBA required for enclosed spaces or dust exposure
Isolation: ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
• Contact with molten substance may cause severe burns to skin and eyes.
• Avoid any skin contact.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/2834 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2834 Phosphorous acid Cls8 ERG154 | ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all di | allfirefighter.com/hazmat/un/2834SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/2834
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Frequently Asked Questions about UN 2834
TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Corrosives in contact with metals may evolve flammable hydrogen gas.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level B minimum for spill response; chemical-resistant suit, gloves, boots; SCBA required for enclosed spaces or dust exposure
Water reactivity: Dissolves in water releasing heat; forms acidic solution; no violent reaction. Recommended extinguishing: Dry chemical, soda ash, lime; water spray may be used to dilute spills.
ERG Guide 154 recommendation: ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 154 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles.
This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.