☣️ UN 2603 • CLASS 3
UN 2603 — Cycloheptatriene
Placard: Flammable. ERG Guide 131. 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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UN 2603 Quick Details
UN 2603
Product name: Cycloheptatriene
DOT Class: 3
Placard type: Flammable
ERG Guide: 131 (check current ERG)
Initial isolation: ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire, isolate 800m all directions and evacuate 800m
Common Hazards of UN 2603
- TOXIC; may be fatal if inhaled, ingested or absorbed through skin.
- Inhalation or contact with some of these materials will irritate or burn skin and eyes.
- Methyl chloroacetate (UN2295) is an eye irritant/lachrymator (causes flow of tears).
- Fire will produce irritating, corrosive and/or toxic gases.
- Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas.
- Runoff from fire control or dilution water may cause environmental contamination.
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors may form explosive mixtures with air.
Chemical Identity & Physical Properties
| Also known as | 1,3,5-CycloheptatrieneCHTTropilideneCycloheptene trimer |
| CAS Number | 544-25-2 |
| Appearance | Colorless to pale yellow liquid with a characteristic aromatic hydrocarbon odor. Volatile flammable liquid at room temperature. |
| Flash Point | -6C (21F) |
| Boiling Point | 116-118C (241-244F) |
| Vapor Density | 3.2 (heavier than air) |
| Water Reactivity | No significant reaction; insoluble in water, floats on surface |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2603
Extinguishing Media
AFFF foam, alcohol-resistant foam, CO2, dry chemical suitable for Class B fires
PPE Requirements
⚠️ Level B minimum; SCBA required; chemical-resistant gloves and suit; highly toxic by all routes of exposure
Isolation & Evacuation
ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire, isolate 800m all directions and evacuate 800m
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 131).
First Actions for a UN 2603 Incident
- 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 for at least 50 meters (150 feet) in all directions.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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📋 Copy & Share Field Card
UN 2603 — CycloheptatrieneHAZMAT RADIO NOTE — UN 2603
Product: Cycloheptatriene
Class 3 / Flammable / ERG 131
PPE: Level B minimum; SCBA required; chemical-resistant gloves and suit; highly toxic by all routes of exposure
ISOLATION: ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire, isolate 800m all directions and evacuate 800m
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 2603 — Cycloheptatriene
Class: 3 | Placard: Flammable | ERG Guide: 131
Appearance: Colorless to pale yellow liquid with a characteristic aromatic hydrocarbon odor. Volatile flammable liquid at room temperature.
Water Reactivity: No significant reaction; insoluble in water, floats on surface
Extinguishing: AFFF foam, alcohol-resistant foam, CO2, dry chemical suitable for Class B fires
PPE: Level B minimum; SCBA required; chemical-resistant gloves and suit; highly toxic by all routes of exposure
Isolation: ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire, isolate 800m all directions and evacuate 800m
— Key Hazards —
• TOXIC; may be fatal if inhaled, ingested or absorbed through skin.
• Inhalation or contact with some of these materials will irritate or burn skin and eyes.
• Methyl chloroacetate (UN2295) is an eye irritant/lachrymator (causes flow of tears).
— 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/2603 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2603 Cycloheptatriene Cls3 ERG131 | ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire | allfirefighter.com/hazmat/un/2603SMS / 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/2603
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Frequently Asked Questions about UN 2603
TOXIC; may be fatal if inhaled, ingested or absorbed through skin. Inhalation or contact with some of these materials will irritate or burn skin and eyes. Methyl chloroacetate (UN2295) is an eye irritant/lachrymator (causes flow of tears). Fire will produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or asphyxiation, especially when in closed or confined areas. Runoff from fire control or dilution water may cause environmental contamination. HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames. Vapors may form explosive mixtures with air.
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; SCBA required; chemical-resistant gloves and suit; highly toxic by all routes of exposure
Water reactivity: No significant reaction; insoluble in water, floats on surface. Recommended extinguishing: AFFF foam, alcohol-resistant foam, CO2, dry chemical suitable for Class B fires.
ERG Guide 131 recommendation: ERG 131: isolate 50m all directions initially; if tank/rail car involved in fire, isolate 800m all directions and evacuate 800m
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 131 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.