☣️ UN 1559 • CLASS 6
UN 1559 — Arsenic pentoxide
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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 1559 Quick Details
UN 1559
Product name: Arsenic pentoxide
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate 300m downwind
Common Hazards of UN 1559
- Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
- 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
- Containers may explode when heated.
- Runoff may pollute waterways.
Chemical Identity & Physical Properties
| Also known as | Arsenic(V) oxideArsenic anhydrideDiarsenic pentoxideArsentic acid anhydride |
| CAS Number | 1303-28-2 |
| Appearance | White, odorless crystalline solid or amorphous powder. Hygroscopic and gradually absorbs moisture from air. |
| Flash Point | Not applicable (inorganic solid, non-flammable) |
| Boiling Point | Not applicable (decomposes above 315°C/599°F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Dissolves slowly in water forming arsentic acid; no violent reaction but solution is highly toxic |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1559
Extinguishing Media
Use dry chemical, CO2, or dry sand; water spray may be used to keep containers cool
PPE Requirements
⚠️ Level A required for spill response; full encapsulation, SCBA, chemical-resistant suit; avoid all contact
Isolation & Evacuation
ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate 300m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 1559 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.
- 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 1559 — Arsenic pentoxideHAZMAT RADIO NOTE — UN 1559
Product: Arsenic pentoxide
Class 6 / Toxic / ERG 151
PPE: Level A required for spill response; full encapsulation, SCBA, chemical-resistant suit; avoid all contact
ISOLATION: ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate 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 1559 — Arsenic pentoxide
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: White, odorless crystalline solid or amorphous powder. Hygroscopic and gradually absorbs moisture from air.
Water Reactivity: Dissolves slowly in water forming arsentic acid; no violent reaction but solution is highly toxic
Extinguishing: Use dry chemical, CO2, or dry sand; water spray may be used to keep containers cool
PPE: Level A required for spill response; full encapsulation, SCBA, chemical-resistant suit; avoid all contact
Isolation: ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate 300m downwind
— Key Hazards —
• Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
• Avoid any skin contact.
• Fire may produce irritating, corrosive and/or toxic gases.
— 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.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/1559 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1559 Arsenic pentoxide Cls6 ERG151 | ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate | allfirefighter.com/hazmat/un/1559SMS / 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/1559
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Frequently Asked Questions about UN 1559
Highly toxic, may be fatal if inhaled, ingested or absorbed through skin. 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 Containers may explode when heated. Runoff may pollute waterways.
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 A required for spill response; full encapsulation, SCBA, chemical-resistant suit; avoid all contact
Water reactivity: Dissolves slowly in water forming arsentic acid; no violent reaction but solution is highly toxic. Recommended extinguishing: Use dry chemical, CO2, or dry sand; water spray may be used to keep containers cool.
ERG Guide 151 recommendation: ERG 151: isolate spill 25m all directions; for large spill isolate 50m, evacuate 300m downwind
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 151 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.