☣️ UN 3371 • CLASS 3
UN 3371 — 2-Methylbutanal
Placard: Flammable. ERG Guide 129. 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.
UN 3371 is 2-Methylbutanal, assigned to ERG Guide 129. First responders should verify the shipping papers and SDS, isolate the area, and base entry, PPE and control tactics on the product's listed hazards.
Hazard overview: The main hazard is a highly flammable aldehyde liquid with vapors that can travel, collect in low areas, and flash back to ignition sources.
Response guidance: In case of fire, use AFFF foam or dry chemical to extinguish. Evacuate the area and call the fire department.
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UN 3371 Quick Details
UN 3371
Product name: 2-Methylbutanal
DOT Class: 3
Placard type: Flammable
ERG Guide: 129 (check current ERG)
Initial isolation: ERG 129: isolate spill 50m all directions; for large spills isolate 800m downwind
Common Hazards of UN 3371
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
- Vapors may travel to source of ignition and flash back.
- Most vapors are heavier than air and may spread along the ground into low or confined areas.
- Vapor explosion hazard indoors, outdoors or in sewers.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Runoff to sewer may create fire or explosion hazard.
- Containers may explode when heated.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, unpleasant aldehyde odor. Liquid at room temperature.
| Also known as | 2-Methylbutyraldehyde2-MethylbutanalIsovaleraldehyde2-Methyl-1-butanal |
| CAS Number | 96-17-3 |
| Appearance | Colorless to pale yellow liquid with a pungent, unpleasant aldehyde odor. Liquid at room temperature. |
| Flash Point | -7°C (19°F) |
| Boiling Point | 92-93°C (198-199°F) |
| Vapor Density | 3.0 (heavier than air) |
| Water Reactivity | No significant reaction with water; low solubility |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3371
Extinguishing Media
AFFF foam, alcohol-resistant foam, CO2, dry chemical
PPE Requirements
⚠️ Level B minimum with SCBA required; vapor-protective clothing for spills or confined spaces
Level B minimum with SCBA required; vapor-protective clothing for spills or confined spaces.
Isolation & Evacuation
ERG 129: isolate spill 50m all directions; for large spills isolate 800m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 129).
First Actions for a UN 3371 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- 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 for at least 50 meters (150 feet) in all directions.
- Consider initial downwind evacuation for at least 300 meters (1000 feet).
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📋 Copy & Share Field Card
UN 3371 — 2-MethylbutanalHAZMAT RADIO NOTE — UN 3371
Product: 2-Methylbutanal
Class 3 / Flammable / ERG 129
PPE: Level B minimum with SCBA required; vapor-protective clothing for spills or confined spaces
ISOLATION: ERG 129: isolate spill 50m all directions; for large spills isolate 800m 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 3371 — 2-Methylbutanal
Class: 3 | Placard: Flammable | ERG Guide: 129
Appearance: Colorless to pale yellow liquid with a pungent, unpleasant aldehyde odor. Liquid at room temperature.
Water Reactivity: No significant reaction with water; low solubility
Extinguishing: AFFF foam, alcohol-resistant foam, CO2, dry chemical
PPE: Level B minimum with SCBA required; vapor-protective clothing for spills or confined spaces
Isolation: ERG 129: isolate spill 50m all directions; for large spills isolate 800m downwind
— Key Hazards —
• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
• Vapors may form explosive mixtures with air.
• Vapors may travel to source of ignition and flash back.
— First Actions —
• CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
• 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/methylbutanal-un-3371 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3371 2-Methylbutanal Cls3 ERG129 | allfirefighter.com/hazmat/un/methylbutanal-un-3371SMS / 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/methylbutanal-un-3371
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Frequently Asked Questions about UN 3371
UN 3371 is 2-Methylbutanal. It is assigned to ERG Guide 129 for initial emergency response.
Yes. It is a highly flammable aldehyde liquid and vapors can form explosive mixtures with air.
Use AFFF or alcohol-resistant foam, dry chemical or CO2. Water fog may be used to cool containers from a safe distance.
Use SCBA and vapor-protective clothing for spills, confined spaces or fire involvement.
It is a colorless to pale yellow liquid with a pungent aldehyde odor.
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.