☣️ UN 3550 • CLASS 6
UN 3550 — Cobalt dihydroxide powder
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ Verification required:
Broad or variable material category; verify exact product, SDS and shipping papers.
⚠️ 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.
UN 3550 is Cobalt dihydroxide powder, assigned to ERG Guide 151. This entry should be verified with shipping papers, labels and the SDS before responders commit to close-range action.
Hazard overview: Cobalt dihydroxide powder presents toxic exposure hazards by inhalation, ingestion or skin contact. Dust, vapor, smoke or contaminated runoff may create additional health and environmental risks.
Response guidance: Use ERG Guide 151, confirm the exact contents, isolate the area, keep unauthorized personnel away, control ignition sources and choose extinguishing agents based on the article or material involved.
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UN 3550 Quick Details
UN 3550
Product name: Cobalt dihydroxide powder
DOT Class: 6
Placard type: Toxic
ERG Guide: 151 (check current ERG)
Initial isolation: ERG 151: Initial isolation 25m in all directions; spill: 25m day/50m night; fire: isolate 800m if tank/rail car involved
Common Hazards of UN 3550
- 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
Pink to blue-violet powder, odorless. Exists as a solid at room temperature, may vary from rose-red to blue depending on hydration state.
| Also known as | Cobalt(II) hydroxideCobaltous hydroxideCobalt hydroxideCobalt dihydroxide |
| CAS Number | 1307-96-6 |
| Appearance | Pink to blue-violet powder, odorless. Exists as a solid at room temperature, may vary from rose-red to blue depending on hydration state. |
| Flash Point | Not applicable (non-combustible inorganic solid) |
| Boiling Point | Not applicable (decomposes before boiling at approximately 168°C) |
| Vapor Density | Not applicable (solid, non-volatile) |
| Water Reactivity | Slightly soluble in water, no violent reaction. May slowly dissolve in acidic conditions. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3550
Extinguishing Media
Water spray for dust control, dry chemical, CO2 for surrounding fires. Avoid generating dust clouds.
PPE Requirements
⚠️ Level B minimum for spill response; SCBA required in enclosed spaces or fire conditions. Impervious gloves, chemical-resistant clothing to prevent skin contact. Avoid inhalation of dust.
Level B minimum for spill response; SCBA required in enclosed spaces or fire conditions. Impervious gloves, chemical-resistant clothing to prevent skin contact. Avoid inhalation of dust. Select final PPE using ERG guidance, SDS, monitoring and incident command.
Isolation & Evacuation
ERG 151: Initial isolation 25m in all directions; spill: 25m day/50m night; fire: isolate 800m if tank/rail car involved
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 151).
First Actions for a UN 3550 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 3550 — Cobalt dihydroxide powderHAZMAT RADIO NOTE — UN 3550
Product: Cobalt dihydroxide powder
Class 6 / Toxic / ERG 151
PPE: Level B minimum for spill response; SCBA required in enclosed spaces or fire conditions. Impervious gloves, chemical-resistant clothing to prevent skin contact. Avoid inhalation of dust.
ISOLATION: ERG 151: Initial isolation 25m in all directions; spill: 25m day/50m night; fire: isolate 800m if tank/rail car involved
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 3550 — Cobalt dihydroxide powder
Class: 6 | Placard: Toxic | ERG Guide: 151
Appearance: Pink to blue-violet powder, odorless. Exists as a solid at room temperature, may vary from rose-red to blue depending on hydration state.
Water Reactivity: Slightly soluble in water, no violent reaction. May slowly dissolve in acidic conditions.
Extinguishing: Water spray for dust control, dry chemical, CO2 for surrounding fires. Avoid generating dust clouds.
PPE: Level B minimum for spill response; SCBA required in enclosed spaces or fire conditions. Impervious gloves, chemical-resistant clothing to prevent skin contact. Avoid inhalation of dust.
Isolation: ERG 151: Initial isolation 25m in all directions; spill: 25m day/50m night; fire: isolate 800m if tank/rail car involved
— 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/cobalt-dihydroxide-powder-un-3550 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3550 Cobalt dihydroxide powder Cls6 ERG151 | allfirefighter.com/hazmat/un/cobalt-dihydroxide-powder-un-3550SMS / 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/cobalt-dihydroxide-powder-un-3550
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Frequently Asked Questions about UN 3550
UN 3550 is Cobalt dihydroxide powder, assigned to ERG Guide 151.
ERG Guide 151 applies for initial isolation, protective actions and first response guidance.
Cobalt dihydroxide powder presents toxic exposure hazards by inhalation, ingestion or skin contact.
Level B minimum for spill response; SCBA required in enclosed spaces or fire conditions. Impervious gloves, chemical-resistant clothing to prevent skin contact. Avoid inhalation of dust.
ERG 151: Initial isolation 25m in all directions; spill: 25m day/50m night; fire: isolate 800m if tank/rail car involved.
Water compatibility depends on the specific contents and incident conditions. Check ERG 151, SDS and incident command before applying water.
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.