☣️ UN 3403 • CLASS 4
Potassium metal alloys, solid
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.
Advertisement
Quick details
UN 3403
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: Initial isolation 50m in all directions. Protective action distance up to 300m downwind for large spills. Evacuate immediate area if fire develops.
Chemical & Response Details
| Also known as | Potassium alloysPotassium-sodium alloy (NaK)Alkali metal alloys containing potassium |
| Appearance | Silvery-white soft metallic solid or semi-liquid alloy. May have a metallic sheen. Typically stored under inert gas or mineral oil to prevent atmospheric contact. |
| Flash Point | Not applicable (ignites spontaneously on contact with water or moist air) |
| Boiling Point | Varies by alloy composition, typically 700-900C (1292-1652F) |
| Vapor Density | Not applicable (solid/semi-liquid at room temperature) |
| Water Reactivity | Reacts violently and explosively with water, producing flammable hydrogen gas and heat. May ignite spontaneously. Never use water. |
| Extinguishing | Dry chemical (G-1 or Met-L-X powder), dry sand, dry graphite powder. No water, no foam, no CO2. |
| PPE | ⚠️ Level B minimum with full face SCBA. Chemical-resistant suit required. Avoid all moisture contact. Work in dry, inert atmosphere if possible. |
| Isolation | ERG 138: Initial isolation 50m in all directions. Protective action distance up to 300m downwind for large spills. Evacuate immediate area if fire develops. |
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).
Advertisement
📋 Copy & Share
UN 3403 — Potassium metal alloys, solid HAZMAT RADIO NOTE — UN 3403
Product: Potassium metal alloys, solid
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with full face SCBA. Chemical-resistant suit required. Avoid all moisture contact. Work in dry, inert atmosphere if possible.
ISOLATION: ERG 138: Initial isolation 50m in all directions. Protective action distance up to 300m downwind for large spills. Evacuate immediate area if fire develops.
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 3403 — Potassium metal alloys, solid
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Silvery-white soft metallic solid or semi-liquid alloy. May have a metallic sheen. Typically stored under inert gas or mineral oil to prevent atmospheric contact.
Water Reactivity: Reacts violently and explosively with water, producing flammable hydrogen gas and heat. May ignite spontaneously. Never use water.
Extinguishing: Dry chemical (G-1 or Met-L-X powder), dry sand, dry graphite powder. No water, no foam, no CO2.
PPE: Level B minimum with full face SCBA. Chemical-resistant suit required. Avoid all moisture contact. Work in dry, inert atmosphere if possible.
Isolation: ERG 138: Initial isolation 50m in all directions. Protective action distance up to 300m downwind for large spills. Evacuate immediate area if fire develops.
— 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/3403 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3403 Potassium metal alloys, solid Cls4 ERG138 | allfirefighter.com/hazmat/un/3403SMS / 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/3403
Advertisement
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 suit required. Avoid all moisture contact. Work in dry, inert atmosphere if possible.
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.