UN 3495 — Iodine
Placard: Corrosive. ERG Guide 154. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3495 is Iodine, a Class 8 hazardous material assigned to ERG Guide 154. Responders should confirm the exact product, container condition and exposure hazards before entry.
Hazard overview: Primary hazards include toxic exposure, corrosive burns, fire or vapor ignition. Iodine may release irritating, toxic or corrosive vapors when heated, spilled or involved in fire, so avoid contact, inhalation and incompatible materials.
Response guidance: For a UN 3495 incident, establish incident command, isolate the area, stay upwind and uphill, keep unauthorized personnel away, verify shipping papers/SDS and follow ERG 154. Use extinguishing, cooling, containment and decontamination tactics only when compatible with the material and local SOP.
Firefighter training notes: Training should emphasize iodine sublimation, heavy vapor behavior, eye and respiratory irritation, and contamination control for crystals or dust. Common tactical errors include assuming a solid has no vapor hazard, entering poorly ventilated areas without respiratory protection, spreading dry crystals during cleanup and overlooking runoff or drain contamination. Incident command should coordinate isolation, ventilation, air monitoring, PPE selection and decontamination with hazmat personnel under local SOP.
Regulatory context: Iodine is regulated as a Class 8 corrosive hazardous material for transportation and emergency response purposes. Workplace exposure, spill reporting and environmental controls may apply depending on quantity, release conditions and jurisdiction. Responders should verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, state or local authority guidance.
Storage & handling: Iodine should be stored in tightly closed compatible containers in a cool, dry and well-ventilated area. Keep it away from ammonia, reducing agents, strong bases, powdered metals, incompatible organics and materials that may react with iodine. Containers should be protected from heat, moisture, breakage and conditions that allow vapor buildup.
UN 3495 Quick Details
Common Hazards of UN 3495
- TOXIC and/or CORROSIVE; inhalation, ingestion or skin and eye contact with material or vapor may cause severe injury.
- Avoid skin and eye contact; iodine can irritate or burn exposed tissue.
- Iodine sublimes readily and may release irritating violet vapors at room temperature or when heated.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive or toxic and may cause environmental contamination.
- Non-combustible solid; substance itself does not readily burn but may decompose or release hazardous vapors when heated.
- Some iodine-containing contamination may react with reducing agents, ammonia, metals or other incompatible materials.
- Vapors are much heavier than air and may accumulate in low or poorly ventilated areas.
Chemical Identity & Physical Properties
Bluish-black to violet-black crystalline solid or lustrous plates with a sharp, characteristic pungent odor. Sublimes readily at room temperature producing violet vapor.
| Also known as | Molecular iodineI2DiiodineIodine crystalsIodine sublimed |
| CAS Number | 7553-56-2 |
| Appearance | Bluish-black to violet-black crystalline solid or lustrous plates with a sharp, characteristic pungent odor. Sublimes readily at room temperature producing violet vapor. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | 184C (363F) - sublimes readily below boiling point |
| Vapor Density | 8.8 (much heavier than air) |
| Water Reactivity | Slightly soluble in water, no significant reaction but forms acidic solution |
Fireground Response Guidance — UN 3495
Extinguishing Media
PPE Requirements
Level B minimum with full-face respirator or SCBA; chemical-resistant suit, gloves, and boots required; avoid all skin and eye contact
Isolation & Evacuation
First Actions for a UN 3495 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing iodine vapor, dust or fumes.
- Do not touch damaged containers or spilled material unless properly trained and wearing appropriate protective equipment.
- Prevent dust generation and avoid spreading crystals or contaminated residue.
- Ventilate closed spaces before entering, but only if properly trained, equipped and authorized by incident command.
- Isolate the spill or leak area in all directions for at least 25 meters (75 feet) for solids.
- For highlighted materials, consult ERG Table 1 for Initial Isolation and Protective Action Distances.
- For non-highlighted materials, increase the immediate precautionary distance as needed in the downwind direction based on vapor, dust or fire conditions.
📋 Copy & Share Field Card
UN 3495 — IodineUse 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.