☣️ UN 2578 • CLASS 8
Phosphorus trioxide
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 2578
Class: 8
Placard type: Corrosive
ERG: Guide 157 (check current ERG)
Isolation: ERG 157: isolate spill 25m all directions; if fire or water-reactive release, initial isolation 100m, protective action 300m downwind
Chemical & Response Details
| 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 |
| Extinguishing | Dry chemical, dry sand, soda ash; avoid water-based agents |
| PPE | ⚠️ Level B minimum; SCBA required; full chemical protective suit for spill response; avoid skin and eye contact |
| Isolation | ERG 157: isolate spill 25m all directions; if fire or water-reactive release, initial isolation 100m, protective action 300m downwind |
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 contact (skin, eyes) with vapors, dusts or substance
- Reaction with water or moist air may release toxic, corrosive or flammable gases.
- Reaction with water may generate much heat that will increase the concentration of fumes in the air.
- Fire will 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
- UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above
- Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
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 2578 — Phosphorus trioxide HAZMAT RADIO NOTE — UN 2578
Product: Phosphorus trioxide
Class 8 / Corrosive / ERG 157
PPE: Level B minimum; SCBA required; full chemical protective suit for spill response; avoid skin and eye contact
ISOLATION: ERG 157: isolate spill 25m all directions; if fire or water-reactive release, initial isolation 100m, protective action 300m downwind
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 2578 — Phosphorus trioxide
Class: 8 | Placard: Corrosive | ERG Guide: 157
Appearance: White to yellowish crystalline solid or powder. Garlic-like or unpleasant odor. Deliquescent, meaning it absorbs moisture from air.
Water Reactivity: Reacts with water to form phosphorous acid (H3PO3), generating heat and toxic fumes
Extinguishing: Dry chemical, dry sand, soda ash; avoid water-based agents
PPE: Level B minimum; SCBA required; full chemical protective suit for spill response; avoid skin and eye contact
Isolation: ERG 157: isolate spill 25m all directions; if fire or water-reactive release, initial isolation 100m, protective action 300m downwind
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
• Reaction with water or moist air may release toxic, corrosive or flammable gases.
• Reaction with water may generate much heat that will increase the concentration of fumes in the air.
— 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/2578 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2578 Phosphorus trioxide Cls8 ERG157 | ERG 157: isolate spill 25m all directions; if fire or water-reactive release, in | allfirefighter.com/hazmat/un/2578SMS / 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/2578
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FAQ
TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance Reaction with water or moist air may release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will 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 UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
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; SCBA required; full chemical protective suit for spill response; avoid skin and eye contact
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 157 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.