UN 2844 — Calcium manganese silicon
Placard: Dangerous When Wet. ERG Guide 138. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2844 is Calcium manganese silicon, a dangerous-when-wet alloy assigned to ERG Guide 138. Moisture can release flammable gas and cause ignition.
Hazard overview: DANGEROUS WHEN WET metal/silicon alloy; water or moisture can release flammable gas. Generated hydrogen or silane-type gases may ignite or form explosive mixtures with air. Finely divided material may ignite from heat, sparks, friction or moisture.
Response guidance: For UN 2844, isolate the area, exclude water/moisture and use SCBA. Use only compatible dry media, watch for re-ignition and verify tactics with SDS and ERG 138.
Firefighter training notes: Training for UN 2844 should emphasize water/moisture exclusion, dry-media tactics, re-ignition checks, gas monitoring, SCBA use and runoff control. Use ERG 138, SDS and local SOP.
Regulatory context: Calcium manganese silicon is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Calcium manganese silicon should be stored dry in sealed compatible containers away from water, moisture, acids, oxidizers and ignition sources. Keep compatible dry media available.
UN 2844 Quick Details
Common Hazards of UN 2844
- DANGEROUS WHEN WET metal/silicon alloy; water or moisture can release flammable gas.
- Generated hydrogen or silane-type gases may ignite or form explosive mixtures with air.
- Finely divided material may ignite from heat, sparks, friction or moisture.
- Water, foam and CO2 can worsen the reaction or spread burning material.
- Fire may produce metal oxides, silicon oxides and irritating/toxic smoke.
- Runoff may create fire, explosion and caustic contamination hazards.
- Containers may rupture when heated or contaminated with moisture.
Chemical Identity & Physical Properties
Silvery-gray to dark gray metallic solid or granules with a metallic appearance. Odorless metallic alloy typically supplied as lumps, granules, or powder.
| Also known as | Calcium manganese silicon alloySilico-manganese-calciumCa-Mn-Si alloyFerroalloy calcium manganese silicon |
| Appearance | Silvery-gray to dark gray metallic solid or granules with a metallic appearance. Odorless metallic alloy typically supplied as lumps, granules, or powder. |
| Flash Point | Not applicable (metallic solid) |
| Boiling Point | Not applicable (metallic alloy, decomposes at high temperature) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts with water or moisture to produce flammable hydrogen gas and may ignite spontaneously. Violent reaction with water produces heat and flammable gases. |
Fireground Response Guidance — UN 2844
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and dry compatible protective clothing. Protect against fire, caustic/reactive dust and toxic decomposition products; exclude moisture.
Isolation & Evacuation
First Actions for a UN 2844 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Keep water or moisture contact controlled because reaction or re-ignition hazards may be severe.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Prevent contaminated liquid, dust, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 138, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2844 — Calcium manganese siliconUse 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.