☣️ 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.
Mercury oxycyanide, desensitized is a highly toxic substance that can cause severe health effects if not handled properly. It is essential to take immediate action in case of an emergency.
Hazard overview: Mercury oxycyanide, desensitized is highly toxic and may be fatal if inhaled, ingested or absorbed through skin. It is also highly toxic if ingested or absorbed through skin.
Response guidance: In case of an emergency, evacuate the area immediately and provide medical attention if exposed. Wear Level A with full encapsulation, SCBA and chemical-resistant gloves to prevent exposure.
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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
Mercury oxycyanide, desensitized is a white to yellowish crystalline solid or powder with odorless or faint characteristic odor and is stable at room temperature when desensitized.
| 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
Wear Level A with full encapsulation, SCBA and chemical-resistant gloves to prevent exposure to mercury oxycyanide, desensitized.
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
- 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 —
• 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/mercury-oxycyanide-desensitized-un-1642 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN1642 Mercury oxycyanide, desensitized Cls6 ERG151 | allfirefighter.com/hazmat/un/mercury-oxycyanide-desensitized-un-1642SMS / 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/mercury-oxycyanide-desensitized-un-1642
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Frequently Asked Questions about UN 1642
No, UN 1642 Mercury oxycyanide, desensitized 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.