☣️ UN 1642 • CLASS 6
UN 1642 — Mercury oxycyanide, desensitized
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.
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UN 1642 Quick Details
UN 1642
Product name: Mercury oxycyanide, desensitized
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: Isolate spill/leak area immediately for at least 100m in all directions; increase isolation if fire involved; evacuate immediate area and consider evacuation of downwind areas
Common Hazards of UN 1642
- 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 | Mercury(II) oxycyanideMercuric oxycyanideMercury oxide cyanideOxycyanomercury |
| CAS Number | 1335-31-5 |
| Appearance | White to yellowish crystalline solid or powder. Odorless or faint characteristic odor. Stable at room temperature when desensitized. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | Decomposes before boiling at elevated temperatures |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Slightly soluble in water; hydrolyzes slowly releasing toxic mercury and cyanide compounds |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1642
Extinguishing Media
Dry chemical, sand, CO2; avoid water spray due to toxicity concerns
PPE Requirements
⚠️ Level A required; full encapsulation, SCBA, chemical-resistant gloves; no skin contact allowed due to extreme toxicity
Isolation & Evacuation
ERG 151: Isolate spill/leak area immediately for at least 100m in all directions; increase isolation if fire involved; evacuate immediate area and consider evacuation of downwind areas
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 1642 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 1642 — Mercury oxycyanide, desensitizedHAZMAT RADIO NOTE — UN 1642
Product: Mercury oxycyanide, desensitized
Class 6 / Toxic / ERG 151
PPE: Level A required; full encapsulation, SCBA, chemical-resistant gloves; no skin contact allowed due to extreme toxicity
ISOLATION: ERG 151: Isolate spill/leak area immediately for at least 100m in all directions; increase isolation if fire involved; evacuate immediate area and consider evacuation of downwind areas
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 1642 — Mercury oxycyanide, desensitized
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: White to yellowish crystalline solid or powder. Odorless or faint characteristic odor. Stable at room temperature when desensitized.
Water Reactivity: Slightly soluble in water; hydrolyzes slowly releasing toxic mercury and cyanide compounds
Extinguishing: Dry chemical, sand, CO2; avoid water spray due to toxicity concerns
PPE: Level A required; full encapsulation, SCBA, chemical-resistant gloves; no skin contact allowed due to extreme toxicity
Isolation: ERG 151: Isolate spill/leak area immediately for at least 100m in all directions; increase isolation if fire involved; evacuate immediate area and consider evacuation of downwind areas
— 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/1642 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1642 Mercury oxycyanide, desensitized Cls6 ERG151 | allfirefighter.com/hazmat/un/1642SMS / 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/1642
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Frequently Asked Questions about UN 1642
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; full encapsulation, SCBA, chemical-resistant gloves; no skin contact allowed due to extreme toxicity
Water reactivity: Slightly soluble in water; hydrolyzes slowly releasing toxic mercury and cyanide compounds. Recommended extinguishing: Dry chemical, sand, CO2; avoid water spray due to toxicity concerns.
ERG Guide 151 recommendation: ERG 151: Isolate spill/leak area immediately for at least 100m in all directions; increase isolation if fire involved; evacuate immediate area and consider evacuation of downwind areas
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.