☣️ UN 2834 • CLASS 8
Phosphorous acid
Placard: Corrosive. 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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Quick details
UN 2834
Class: 8
Placard type: Corrosive
ERG: Guide 154 (check current ERG)
Isolation: ERG 154: Small spill isolate 30m all directions; Large spill isolate 100m all directions; Consider evacuation 300m downwind if large spill
Chemical & Response Details
| 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 |
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
First actions (field-minded)
- 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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UN 2834 — Phosphorous acid HAZMAT 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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FAQ
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
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.