☣️ UN 1859 • CLASS 2
UN 1859 — Silicon tetrafluoride, compressed
Placard: Toxic Gas. ERG Guide 125. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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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UN 1859 Quick Details
UN 1859
Product name: Silicon tetrafluoride, compressed
DOT Class: 2
Placard type: Toxic Gas
ERG Guide: 125 (check current ERG)
Initial isolation: ERG 125: Initial isolation 100m all directions; Protective Action Distance 300m downwind daytime (800m nighttime) for small spills
Common Hazards of UN 1859
- 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.
Chemical Identity & Physical Properties
| Also known as | Silicon tetrafluorideTetrafluorosilaneSiF4Silicon fluoride |
| CAS Number | 7783-61-1 |
| Appearance | Colorless gas with a pungent, suffocating odor. Fumes strongly in moist air forming white clouds of silica and hydrofluoric acid. |
| Flash Point | Not applicable (non-flammable gas) |
| Boiling Point | -86C (-123F) |
| Vapor Density | 3.6 (heavier than air) |
| Water Reactivity | Reacts violently with water producing highly toxic and corrosive hydrofluoric acid and silicic acid fumes |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1859
Extinguishing Media
Dry chemical, CO2, inert gas; do not use water or aqueous agents
PPE Requirements
⚠️ Level A or B required; full-face SCBA, chemical-resistant suit, neoprene or Viton gloves; avoid contact with liquefied gas (frostbite hazard)
Isolation & Evacuation
ERG 125: Initial isolation 100m all directions; Protective Action Distance 300m downwind daytime (800m nighttime) for small spills
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 125).
First Actions for a UN 1859 Incident
- 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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📋 Copy & Share Field Card
UN 1859 — Silicon tetrafluoride, compressedHAZMAT RADIO NOTE — UN 1859
Product: Silicon tetrafluoride, compressed
Class 2 / Toxic Gas / ERG 125
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, neoprene or Viton gloves; avoid contact with liquefied gas (frostbite hazard)
ISOLATION: ERG 125: Initial isolation 100m all directions; Protective Action Distance 300m downwind daytime (800m nighttime) for small spills
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 1859 — Silicon tetrafluoride, compressed
Class: 2 | Placard: Toxic Gas | ERG Guide: 125
Appearance: Colorless gas with a pungent, suffocating odor. Fumes strongly in moist air forming white clouds of silica and hydrofluoric acid.
Water Reactivity: Reacts violently with water producing highly toxic and corrosive hydrofluoric acid and silicic acid fumes
Extinguishing: Dry chemical, CO2, inert gas; do not use water or aqueous agents
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, neoprene or Viton gloves; avoid contact with liquefied gas (frostbite hazard)
Isolation: ERG 125: Initial isolation 100m all directions; Protective Action Distance 300m downwind daytime (800m nighttime) for small spills
— 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/1859 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1859 Silicon tetrafluoride, compressed Cls2 ERG125 | allfirefighter.com/hazmat/un/1859SMS / 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/1859
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Frequently Asked Questions about UN 1859
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 required; full-face SCBA, chemical-resistant suit, neoprene or Viton gloves; avoid contact with liquefied gas (frostbite hazard)
Water reactivity: Reacts violently with water producing highly toxic and corrosive hydrofluoric acid and silicic acid fumes. Recommended extinguishing: Dry chemical, CO2, inert gas; do not use water or aqueous agents.
ERG Guide 125 recommendation: ERG 125: Initial isolation 100m all directions; Protective Action Distance 300m downwind daytime (800m nighttime) for small spills
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.