☣️ UN 2194 • CLASS 2
Selenium hexafluoride
Placard: Toxic Gas. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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Quick details
UN 2194
Class: 2
Placard type: Toxic Gas
ERG: Guide 125 (check current ERG)
Isolation: ERG 125: initially isolate 100m in all directions; protect persons downwind; increase isolation distance for large spills or fires
Chemical & Response Details
| Also known as | Selenium fluorideSelenium(VI) fluorideSeF6 |
| CAS Number | 7783-79-1 |
| Appearance | Colorless gas with a repulsive odor. Exists as a gas at room temperature and normal atmospheric pressure. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | -34.5C (-30.1F) |
| Vapor Density | 6.4 (heavier than air) |
| Water Reactivity | Reacts slowly with moisture to form toxic and corrosive hydrogen fluoride and selenium compounds |
| Extinguishing | Not applicable for firefighting; use water spray to cool containers from distance |
| PPE | ⚠️ Level A or B minimum; full-face SCBA required; chemical-resistant suit for liquid contact; prevent skin contact with liquefied gas |
| Isolation | ERG 125: initially isolate 100m in all directions; protect persons downwind; increase isolation distance for large spills or fires |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin.
- Vapors are extremely irritating and corrosive.
- Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may cause environmental contamination.
- Some may burn but none ignite readily.
- Vapors from liquefied gas are initially heavier than air and spread along ground.
- Some of these materials may react violently with water.
First actions (field-minded)
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Many gases are heavier than air and will spread along the ground and collect in low or confined areas
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area for at least 100 meters (330 feet) in all directions.
- 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
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UN 2194 — Selenium hexafluoride HAZMAT RADIO NOTE — UN 2194
Product: Selenium hexafluoride
Class 2 / Toxic Gas / ERG 125
PPE: Level A or B minimum; full-face SCBA required; chemical-resistant suit for liquid contact; prevent skin contact with liquefied gas
ISOLATION: ERG 125: initially isolate 100m in all directions; protect persons downwind; increase isolation distance for large spills or fires
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 2194 — Selenium hexafluoride
Class: 2 | Placard: Toxic Gas | ERG Guide: 125
Appearance: Colorless gas with a repulsive odor. Exists as a gas at room temperature and normal atmospheric pressure.
Water Reactivity: Reacts slowly with moisture to form toxic and corrosive hydrogen fluoride and selenium compounds
Extinguishing: Not applicable for firefighting; use water spray to cool containers from distance
PPE: Level A or B minimum; full-face SCBA required; chemical-resistant suit for liquid contact; prevent skin contact with liquefied gas
Isolation: ERG 125: initially isolate 100m in all directions; protect persons downwind; increase isolation distance for large spills or fires
— Key Hazards —
• TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin.
• Vapors are extremely irritating and corrosive.
• Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Many gases are heavier than air and will spread along the ground and collect in low or confined areas
SOURCE: allfirefighter.com/hazmat/un/2194 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2194 Selenium hexafluoride Cls2 ERG125 | ERG 125: initially isolate 100m in all directions; protect persons downwind; inc | allfirefighter.com/hazmat/un/2194SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions. Page: https://allfirefighter.com/hazmat/un/2194
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FAQ
TOXIC and/or CORROSIVE; may be fatal if inhaled, ingested or absorbed through skin. Vapors are extremely irritating and corrosive. Contact with gas or liquefied gas may cause burns, severe injury and/or frostbite. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may cause environmental contamination. Some may burn but none ignite readily. Vapors from liquefied gas are initially heavier than air and spread along ground. Some of these materials may react violently with water.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level A or B minimum; full-face SCBA required; chemical-resistant suit for liquid contact; prevent skin contact with liquefied gas
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 125 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles. This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.