☣️ UN 1641 • CLASS 6
Mercury oxide
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 1641
Class: 6
Placard type: Toxic
ERG: Guide 151 (check current ERG)
Isolation: ERG 151: Initial isolation 50m in all directions; protective action distance up to 300m downwind for large spills
Chemical & Response Details
| Also known as | Mercuric oxideMercury(II) oxideRed mercury oxideYellow mercury oxideHydrargyri oxidum rubrum |
| CAS Number | 21908-53-2 |
| Appearance | Heavy crystalline powder, typically red or yellow-orange in color, odorless. Solid at room temperature with high density. |
| Flash Point | Not applicable (non-combustible solid) |
| Boiling Point | Not applicable (decomposes at approximately 500C/932F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Slightly soluble in water with minimal reaction; may form alkaline solution |
| Extinguishing | Water spray, CO2, dry chemical suitable; no special restrictions on extinguishing media |
| PPE | ⚠️ Level B minimum with full-face respirator and SCBA; impervious gloves and suit required to prevent skin contact due to extreme toxicity |
| Isolation | ERG 151: Initial isolation 50m in all directions; protective action distance up to 300m downwind for large spills |
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 1641 — Mercury oxide HAZMAT RADIO NOTE — UN 1641
Product: Mercury oxide
Class 6 / Toxic / ERG 151
PPE: Level B minimum with full-face respirator and SCBA; impervious gloves and suit required to prevent skin contact due to extreme toxicity
ISOLATION: ERG 151: Initial isolation 50m in all directions; protective action distance up to 300m downwind for large spills
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 1641 — Mercury oxide
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: Heavy crystalline powder, typically red or yellow-orange in color, odorless. Solid at room temperature with high density.
Water Reactivity: Slightly soluble in water with minimal reaction; may form alkaline solution
Extinguishing: Water spray, CO2, dry chemical suitable; no special restrictions on extinguishing media
PPE: Level B minimum with full-face respirator and SCBA; impervious gloves and suit required to prevent skin contact due to extreme toxicity
Isolation: ERG 151: Initial isolation 50m in all directions; protective action distance up to 300m downwind for large spills
— 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/1641 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1641 Mercury oxide Cls6 ERG151 | ERG 151: Initial isolation 50m in all directions; protective action distance up | allfirefighter.com/hazmat/un/1641SMS / 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/1641
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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 B minimum with full-face respirator and SCBA; impervious gloves and suit required to prevent skin contact due to extreme toxicity
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.