☣️ UN 2257 • CLASS 4
Potassium
Placard: Dangerous When Wet. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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 2257
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: Initial isolation 50m in all directions. If fire or spill is large, isolate 800m in all directions. Evacuate downwind areas if involved in fire.
Chemical & Response Details
| Also known as | KaliumPotassium metalK |
| CAS Number | 7440-09-7 |
| Appearance | Soft, silvery-white metal with a waxy appearance. Rapidly tarnishes in air forming a gray oxide coating. Highly reactive, must be stored under mineral oil or inert gas. |
| Flash Point | Not applicable (pyrophoric metal) |
| Boiling Point | 759C (1398F) |
| Vapor Density | Not applicable (solid metal) |
| Water Reactivity | Reacts violently with water, producing flammable hydrogen gas and potassium hydroxide. May ignite spontaneously on contact with water or moist air. |
| Extinguishing | Dry powder (sodium chloride or graphite-based Class D extinguisher), dry sand, soda ash. Never use water, foam, CO2, or halogenated agents. |
| PPE | ⚠️ Level B minimum with full face SCBA; chemical-resistant gloves and suit. Handle only under inert atmosphere or mineral oil. Extreme reactivity with moisture requires strict exclusion of water. |
| Isolation | ERG 138: Initial isolation 50m in all directions. If fire or spill is large, isolate 800m in all directions. Evacuate downwind areas if involved in fire. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Produce flammable gases on contact with water.
- May ignite on contact with water or moist air.
- Some react vigorously or explosively on contact with water.
- May be ignited by heat, sparks or flames.
- May re-ignite after fire is extinguished.
- Some are transported in highly flammable liquids.
- Runoff may create fire or explosion hazard.
- Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
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.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
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UN 2257 — Potassium HAZMAT RADIO NOTE — UN 2257
Product: Potassium
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with full face SCBA; chemical-resistant gloves and suit. Handle only under inert atmosphere or mineral oil. Extreme reactivity with moisture requires strict exclusion of water.
ISOLATION: ERG 138: Initial isolation 50m in all directions. If fire or spill is large, isolate 800m in all directions. Evacuate downwind areas if involved in fire.
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 2257 — Potassium
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Soft, silvery-white metal with a waxy appearance. Rapidly tarnishes in air forming a gray oxide coating. Highly reactive, must be stored under mineral oil or inert gas.
Water Reactivity: Reacts violently with water, producing flammable hydrogen gas and potassium hydroxide. May ignite spontaneously on contact with water or moist air.
Extinguishing: Dry powder (sodium chloride or graphite-based Class D extinguisher), dry sand, soda ash. Never use water, foam, CO2, or halogenated agents.
PPE: Level B minimum with full face SCBA; chemical-resistant gloves and suit. Handle only under inert atmosphere or mineral oil. Extreme reactivity with moisture requires strict exclusion of water.
Isolation: ERG 138: Initial isolation 50m in all directions. If fire or spill is large, isolate 800m in all directions. Evacuate downwind areas if involved in fire.
— Key Hazards —
• Produce flammable gases on contact with water.
• May ignite on contact with water or moist air.
• Some react vigorously or explosively on contact with water.
— 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.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/2257 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2257 Potassium Cls4 ERG138 | ERG 138: Initial isolation 50m in all directions. If fire or spill is large, iso | allfirefighter.com/hazmat/un/2257SMS / 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/2257
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FAQ
Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard. Inhalation or contact with vapors, substance or decomposition products may cause severe injury or
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 SCBA; chemical-resistant gloves and suit. Handle only under inert atmosphere or mineral oil. Extreme reactivity with moisture requires strict exclusion of water.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 138 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.