☣️ UN 1561 • CLASS 6
Arsenic trioxide
Placard: Toxic. 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 1561
Class: 6
Placard type: Toxic
ERG: Guide 151 (check current ERG)
Isolation: ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate area and deny entry
Chemical & Response Details
| 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 |
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
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.
- 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 1561 — Arsenic trioxide HAZMAT 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 —
• 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/1561 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1561 Arsenic trioxide Cls6 ERG151 | ERG 151: isolate spill 25m all directions; large spill 50m; evacuate immediate a | allfirefighter.com/hazmat/un/1561SMS / 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/1561
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FAQ
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 mandatory; avoid any skin contact
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.