UN 0493 — Signals, railway track, explosive
Placard: Explosive 1.4G. ERG Guide 114. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 0493 is Signals, railway track, explosive, a Class 1.4 explosive entry assigned to ERG Guide 114. It presents a limited fire or minor blast hazard, but responders still need isolation, smoke protection and shipment verification.
Hazard overview: UN 0493 generally has effects limited to the package or immediate area, but heat or fire can cause localized deflagration, popping, fragments and irritating smoke. The hazard may increase if other explosives, ammunition or pyrotechnics are nearby.
Response guidance: For a UN 0493 incident, responders should confirm the article or substance using shipping papers, markings and ERG Guide 114. Isolate the area, keep personnel out of smoke, control ignition sources when safe, and expand the perimeter if fire involves larger quantities or adjacent explosives.
Firefighter training notes: Training should emphasize the difference between limited-effect explosives and higher-hazard Class 1 materials. Common errors include standing too close to heated packages, dismissing smoke hazards, disturbing damaged articles and failing to check for adjacent explosives or ammunition.
Regulatory context: Signals, railway track, explosive is regulated as a Class 1 explosive hazardous material. Transportation, storage, quantity limits, fire code controls and reporting requirements may vary by jurisdiction. Responders should verify current requirements through shipping papers, SDS or product documents and applicable DOT, ATF, OSHA, NFPA, military, state or local authority guidance.
Storage & handling: Signals, railway track, explosive should be stored only in approved packaging, magazines or authorized explosive storage areas, separated from ignition sources, incompatible materials and unauthorized access. Packages should be protected from heat, impact, friction, moisture where relevant and physical damage according to product documentation and applicable explosive storage regulations.
UN 0493 Quick Details
Common Hazards of UN 0493
- Minor explosive and fire hazard with effects usually limited to the device or package.
- Smoke, flame or audible output may reduce visibility, irritate the respiratory tract or start nearby fires.
- Localized burning, deflagration, popping or small fragments may occur if heated.
- Low mass explosion risk under normal transport conditions.
- Heated packages may fail and scatter small articles or fragments.
- Nearby explosives, ammunition or pyrotechnics may increase the overall incident hazard.
Chemical Identity & Physical Properties
Small metal or plastic cylindrical devices containing a small explosive charge designed to create a loud report when crushed by a train wheel. Typically wrapped in protective casing.
| Also known as | Railway detonatorsTrack signalsTrack torpedoesRail warning signalsExplosive track devices |
| Appearance | Small metal or plastic cylindrical devices containing a small explosive charge designed to create a loud report when crushed by a train wheel. Typically wrapped in protective casing. |
| Flash Point | Not applicable (explosive device) |
| Boiling Point | Not applicable (explosive device) |
| Vapor Density | Not applicable (solid explosive device) |
| Water Reactivity | No significant reaction with water |
Fireground Response Guidance — UN 0493
Extinguishing Media
PPE Requirements
Structural firefighting protective clothing with SCBA is appropriate for fire or smoke exposure, with distance maintained from heated packages. Approach and handling should follow incident command and local SOP.
Isolation & Evacuation
First Actions for a UN 0493 Incident
- CALL 911. Notify law enforcement if explosive articles, ordnance or blasting components are involved.
- Keep unauthorized personnel away.
- Stage upwind and avoid smoke from burning articles.
- Move unprotected people out of the smoke path when safe and practical.
- Eliminate ignition sources if it is safe to do so.
- Isolate the area and expand the perimeter if fire grows or additional explosives are present.
- Use ERG Guide 114, shipping papers and incident command for isolation and fire response decisions.
📋 Copy & Share Field Card
UN 0493 — Signals, railway track, explosiveUse 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.