☣️ UN 1561 • CLASS 6
UN 1561 — Arsenic trioxide
Placard: Toxic. ERG Guide 151. 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.
Arsenic trioxide is a highly toxic substance that requires immediate attention in case of an emergency. It is essential to follow proper procedures for handling and disposal.
Hazard overview: Arsenic trioxide is highly toxic and may be fatal if inhaled, ingested or absorbed through skin. It is also highly reactive and may cause severe burns to skin and eyes.
Response guidance: In case of an emergency, evacuate the area immediately and deny entry. Use Level A PPE for spill response and follow the ERG 151 guidelines for isolation and cleanup.
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UN 1561 Quick Details
UN 1561
Product name: Arsenic trioxide
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate area and deny entry
Common Hazards of UN 1561
- 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
Arsenic trioxide exists as a white, odorless crystalline powder or solid, and is stable at room temperature.
| Also known as | Arsenous oxideArsenic(III) oxideArsenous acid anhydrideWhite arsenicArsenious oxide |
| CAS Number | 1327-53-3 |
| Appearance | White, odorless crystalline powder or solid. Exists as amorphous or crystalline forms. Stable at room temperature. |
| Flash Point | Not applicable (non-combustible solid) |
| Boiling Point | 465C (869F) - sublimes |
| Vapor Density | Not applicable (solid, but vapors heavier than air when heated) |
| Water Reactivity | Slightly soluble in water, no violent reaction but forms toxic solutions |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1561
Extinguishing Media
Water spray, dry chemical, CO2 - use media appropriate for surrounding fire
PPE Requirements
⚠️ Level A required for spill response; full encapsulation, SCBA mandatory; avoid any skin contact
Level A PPE is required for spill response, including full encapsulation, SCBA, and avoidance of any skin contact.
Isolation & Evacuation
ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate area and deny entry
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 1561 Incident
- 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 1561 — Arsenic trioxideHAZMAT RADIO NOTE — UN 1561
Product: Arsenic trioxide
Class 6 / Toxic / ERG 151
PPE: Level A required for spill response; full encapsulation, SCBA mandatory; avoid any skin contact
ISOLATION: ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate area and deny entry
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 1561 — Arsenic trioxide
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: White, odorless crystalline powder or solid. Exists as amorphous or crystalline forms. Stable at room temperature.
Water Reactivity: Slightly soluble in water, no violent reaction but forms toxic solutions
Extinguishing: Water spray, dry chemical, CO2 - use media appropriate for surrounding fire
PPE: Level A required for spill response; full encapsulation, SCBA mandatory; avoid any skin contact
Isolation: ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate area and deny entry
— 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 —
• 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.
SOURCE: allfirefighter.com/hazmat/un/arsenic-trioxide-un-1561 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN1561 Arsenic trioxide Cls6 ERG151 | allfirefighter.com/hazmat/un/arsenic-trioxide-un-1561SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/arsenic-trioxide-un-1561
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Frequently Asked Questions about UN 1561
No, Arsenic trioxide is not flammable.
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.