UN 0377 — Primers, cap type
Placard: Explosive 1.1B. ERG Guide 112. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 0377 covers cap-type primers classified as Division 1.1B, representing a mass explosion hazard with extremely sensitive primary explosive compositions enclosed in small metallic brass or aluminum casings. These devices are used to initiate propellant or explosive charges and are among the most sensitive initiating explosives regulated under DOT hazmat rules.
Hazard overview: UN 0377 cap-type primers present a mass explosion risk in which the entire shipment can detonate simultaneously, producing lethal blast overpressure and fragmentation with no warning. The primary explosive contents are highly sensitive to heat, friction, shock, and static electricity, making accidental initiation a serious concern during any emergency response.
Response guidance: Immediately isolate 500 meters in all directions and evacuate downwind to at least 1,600 meters if the material is on fire or involved in an explosion. Do not fight fires involving UN 0377 — personnel should withdraw to the evacuation perimeter, and only dry sand or earth should be considered for isolated small fires, with no water or foam under any circumstances.
UN 0377 Quick Details
Common Hazards of UN 0377
- Mass explosion hazard — entire load may detonate simultaneously.
- Severe blast overpressure and fragmentation.
- Sensitive to heat, shock, and friction.
- Secondary fire and debris hazard.
Chemical Identity & Physical Properties
UN 0377 cap-type primers are small cylindrical metallic devices constructed from brass or aluminum, containing sensitive primary explosive compositions that are highly reactive to thermal and mechanical stimuli.
| Also known as | Percussion capsBlasting capsInitiator capsDetonator primersCap-type primers |
| Appearance | Small metallic cylindrical devices containing primary explosives, typically brass or aluminum construction with sensitive explosive composition inside. |
| Flash Point | Not applicable (explosive article) |
| Boiling Point | Not applicable (explosive article) |
| Vapor Density | Not applicable (solid explosive device) |
| Water Reactivity | No significant reaction with water, but moisture may degrade explosive sensitivity over time |
Fireground Response Guidance — UN 0377
Extinguishing Media
PPE Requirements
Level A with full-face SCBA is required for fire response, with approach from a protected position at maximum standoff distance and no entry into any area where explosive primers are burning.
Isolation & Evacuation
First Actions for a UN 0377 Incident
- CALL 911. Then call emergency response telephone number on shipping paper.
- Establish large isolation zone — minimum 500 meters in all directions.
- Stage upwind, uphill; limit personnel to essential responders only.
- Request Hazmat + law enforcement + additional resources immediately.
- Do not fight fire — evacuate and isolate; let burn if no life safety risk.
- Protect exposures only if safe and directed by command.
- Consult current ERG Guide 112 and follow SOP/SOG.
📋 Copy & Share Field Card
UN 0377 — Primers, cap typeUse 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.