☣️ UN 3148 • CLASS 4
Water-reactive liquid, 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 3148
Class: 4
Placard type: Dangerous When Wet
ERG: Guide 138 (check current ERG)
Isolation: ERG 138: Initial isolation 50m (150 ft) all directions; protect from water/moisture; if fire or spill is large, isolate 800m (0.5 mi) and consider evacuation in downwind direction
Chemical & Response Details
| Also known as | Water-reactive liquid not otherwise specifiedDangerous when wet liquidClass 4.3 liquidUN3148 |
| Appearance | Variable appearance depending on specific substance; typically clear to colored liquid that reacts with water or moisture in air. May emit visible fumes or heat upon contact with moisture. |
| Flash Point | Variable, substance-dependent; many have low flash points below 23C (73F) |
| Boiling Point | Variable, substance-dependent; typically 50-200C (122-392F) range |
| Vapor Density | Variable, substance-dependent; typically heavier than air (>1) |
| Water Reactivity | Reacts vigorously to violently with water, producing flammable gases (often hydrogen or other flammable vapors); may ignite spontaneously on contact with water or moist air |
| Extinguishing | Dry chemical, dry sand, soda ash; DO NOT use water, foam, or CO2 containing moisture |
| PPE | ⚠️ Level B minimum with SCBA required; full chemical-resistant suit if splash hazard; keep all PPE dry; avoid any moisture contact |
| Isolation | ERG 138: Initial isolation 50m (150 ft) all directions; protect from water/moisture; if fire or spill is large, isolate 800m (0.5 mi) and consider evacuation in downwind direction |
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 3148 — Water-reactive liquid, n.o.s. HAZMAT RADIO NOTE — UN 3148
Product: Water-reactive liquid, n.o.s.
Class 4 / Dangerous When Wet / ERG 138
PPE: Level B minimum with SCBA required; full chemical-resistant suit if splash hazard; keep all PPE dry; avoid any moisture contact
ISOLATION: ERG 138: Initial isolation 50m (150 ft) all directions; protect from water/moisture; if fire or spill is large, isolate 800m (0.5 mi) and consider evacuation in downwind direction
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 3148 — Water-reactive liquid, n.o.s.
Class: 4 | Placard: Dangerous When Wet | ERG Guide: 138
Appearance: Variable appearance depending on specific substance; typically clear to colored liquid that reacts with water or moisture in air. May emit visible fumes or heat upon contact with moisture.
Water Reactivity: Reacts vigorously to violently with water, producing flammable gases (often hydrogen or other flammable vapors); may ignite spontaneously on contact with water or moist air
Extinguishing: Dry chemical, dry sand, soda ash; DO NOT use water, foam, or CO2 containing moisture
PPE: Level B minimum with SCBA required; full chemical-resistant suit if splash hazard; keep all PPE dry; avoid any moisture contact
Isolation: ERG 138: Initial isolation 50m (150 ft) all directions; protect from water/moisture; if fire or spill is large, isolate 800m (0.5 mi) and consider evacuation in downwind direction
— 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/3148 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3148 Water-reactive liquid, n.o.s. Cls4 ERG138 | allfirefighter.com/hazmat/un/3148SMS / 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/3148
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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; full chemical-resistant suit if splash hazard; keep all PPE dry; avoid any moisture contact
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.