UN 1622 — Magnesium arsenate
Placard: Toxic. ERG Guide 151. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Magnesium arsenate is a highly toxic substance that can be fatal if inhaled, ingested, or absorbed through skin. It is a white or grayish-white odorless powder or crystalline solid at room temperature.
Hazard overview: Highly toxic, may be fatal if inhaled, ingested or absorbed through skin. Avoid any skin contact.
Response guidance: Isolate spill 25m all directions, evacuate immediate area and downwind if airborne powder suspected. Use water spray, fog, or dry chemical for fire control.
UN 1622 Quick Details
Common Hazards of UN 1622
- Highly toxic, may be fatal if inhaled, ingested or absorbed through skin.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- Containers may explode when heated.
- Runoff may pollute waterways.
Chemical Identity & Physical Properties
White or grayish-white odorless powder or crystalline solid at room temperature. May appear as granules or lumps.
| Also known as | Trimagnesium diarsenateMagnesium arsenate tribasicArsenate of magnesiumMagnesium salt of arsenic acid |
| CAS Number | 7784-36-3 |
| Appearance | White or grayish-white odorless powder or crystalline solid at room temperature. May appear as granules or lumps. |
| Flash Point | Not applicable (inorganic solid, non-flammable) |
| Boiling Point | Not applicable (decomposes before boiling) |
| Vapor Density | Not applicable (solid with negligible vapor pressure) |
| Water Reactivity | Slightly soluble in water; no violent reaction but may release toxic arsenic compounds over time |
Fireground Response Guidance — UN 1622
Extinguishing Media
PPE Requirements
Level B minimum; SCBA mandatory; full chemical-resistant suit required; avoid all skin contact due to extreme toxicity.
Isolation & Evacuation
First Actions for a UN 1622 Incident
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- 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
📋 Copy & Share Field Card
UN 1622 — Magnesium arsenateUse 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.