UN 0403 — Flares, aerial
Placard: Explosive 1.3G. ERG Guide 112. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 0403 aerial flares are cylindrical pyrotechnic devices containing combustible materials and oxidizers designed to produce intense light and heat, classified as Division 1.3G for their fire and fragment projection hazard rather than mass explosion risk. These devices are commonly used for signaling, illumination, and countermeasure applications and may contain water-reactive metals such as magnesium or aluminum as fuel components.
Hazard overview: Ignited UN 0403 flares generate extreme radiant heat and can eject burning fragments at significant velocity, posing ignition and injury hazards well beyond the device itself. Housings containing magnesium or aluminum will react violently with water, producing flammable hydrogen gas and intensifying combustion if water is mistakenly applied.
Response guidance: Per ERG Guide 112, establish an initial isolation zone of 500 meters in all directions and consider evacuating 1,600 meters if cargo is involved in fire. Suppress with dry sand, dry chemical, or soda ash to smother burning devices; if conditions permit, allow flares to burn out in a controlled, isolated area rather than risk a reactive water application.
UN 0403 Quick Details
Common Hazards of UN 0403
- Fire and burning hazard — not mass explosion.
- Intense heat and possible fragment projection.
- May deflagrate and initiate other materials.
- Smoke and toxic combustion products.
Chemical Identity & Physical Properties
Aerial flares are cylindrical metal or plastic-housed pyrotechnic assemblies containing oxidizer-fuel compositions, designed to produce sustained high-intensity light and heat when initiated.
| Also known as | Aerial flaresSignal flaresPyrotechnic flaresIlluminating flaresDistress flares |
| Appearance | Cylindrical pyrotechnic devices containing combustible materials and oxidizers, typically in metal or plastic housings. Designed to produce intense light and heat when ignited. |
| Flash Point | Not applicable (pyrotechnic composition) |
| Boiling Point | Not applicable (pyrotechnic composition) |
| Vapor Density | Not applicable (solid pyrotechnic device) |
| Water Reactivity | May contain water-reactive metals such as magnesium or aluminum; avoid water application on burning flares |
Fireground Response Guidance — UN 0403
Extinguishing Media
PPE Requirements
Wear full protective clothing with positive-pressure SCBA, a face shield, and heat-resistant gloves, and maintain maximum feasible standoff distance due to intense heat output and potential fragment projection.
Isolation & Evacuation
First Actions for a UN 0403 Incident
- CALL 911. Then call emergency response telephone number on shipping paper.
- Isolate area; stage upwind — fire and fragment hazard.
- Request Hazmat + law enforcement.
- Control ignition sources; deny entry.
- Consult current ERG Guide 112 and follow SOP/SOG.
📋 Copy & Share Field Card
UN 0403 — Flares, aerialUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.