☣️ UN 1409 • CLASS 4
Metal hydrides, water-reactive, n.o.s.
Placard: Dangerous When Wet. 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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Quick details
UN 1409
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: Isolate spill area at least 25m (75 ft) in all directions. If fire involves large quantities, isolate 800m (1/2 mile) and evacuate downwind.
Chemical & Response Details
| Also known as | Metal hydridesHydride powdersReactive metal hydridesWater-reactive hydrides |
| Appearance | Typically gray to white powders or crystalline solids, odorless or slight metallic odor. Appears as dry solid material at room temperature. |
| Flash Point | Not applicable (reacts with water to produce flammable hydrogen gas) |
| Boiling Point | Not applicable (decomposes violently in presence of water) |
| Vapor Density | Not applicable (solid material) |
| Water Reactivity | Reacts violently to explosively with water, producing flammable hydrogen gas and heat. May ignite spontaneously on contact with water or moist air. Do not use water. |
| Extinguishing | Dry sand, dry chemical powder, dry graphite powder. DO NOT use water, foam, CO2, or halogenated agents. |
| PPE | ⚠️ Level B minimum with SCBA required. Fully encapsulating suit if airborne dust present. Avoid moisture contact with skin or equipment. |
| Isolation | ERG 138: Isolate spill area at least 25m (75 ft) in all directions. If fire involves large quantities, isolate 800m (1/2 mile) and evacuate downwind. |
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 1409 — Metal hydrides, water-reactive, n.o.s. HAZMAT RADIO NOTE — UN 1409
Product: Metal hydrides, water-reactive, n.o.s.
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with SCBA required. Fully encapsulating suit if airborne dust present. Avoid moisture contact with skin or equipment.
ISOLATION: ERG 138: Isolate spill area at least 25m (75 ft) in all directions. If fire involves large quantities, isolate 800m (1/2 mile) and evacuate downwind.
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 1409 — Metal hydrides, water-reactive, n.o.s.
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Typically gray to white powders or crystalline solids, odorless or slight metallic odor. Appears as dry solid material at room temperature.
Water Reactivity: Reacts violently to explosively with water, producing flammable hydrogen gas and heat. May ignite spontaneously on contact with water or moist air. Do not use water.
Extinguishing: Dry sand, dry chemical powder, dry graphite powder. DO NOT use water, foam, CO2, or halogenated agents.
PPE: Level B minimum with SCBA required. Fully encapsulating suit if airborne dust present. Avoid moisture contact with skin or equipment.
Isolation: ERG 138: Isolate spill area at least 25m (75 ft) in all directions. If fire involves large quantities, isolate 800m (1/2 mile) and evacuate downwind.
— 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/1409 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1409 Metal hydrides, water-reactive, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/1409SMS / 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/1409
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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 SCBA required. Fully encapsulating suit if airborne dust present. Avoid moisture contact with skin or equipment.
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.