☣️ UN 2202 • CLASS 2
UN 2202 — Hydrogen selenide, anhydrous
Placard: Toxic Gas. ERG Guide 117. 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.
Advertisement
UN 2202 Quick Details
UN 2202
Product name: Hydrogen selenide, anhydrous
DOT Class: 2
Placard type: Toxic Gas
ERG Guide: 117 (check current ERG)
Initial isolation: ERG 117: isolate 150m all directions initially; protect from heat and ignition sources; evacuate downwind areas immediately
Common Hazards of UN 2202
- TOXIC; Extremely Hazardous.
- May be fatal if inhaled or absorbed through skin.
- Initial odor may be irritating or foul and may deaden your sense of smell.
- 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.
- These materials are extremely flammable.
- May form explosive mixtures with air.
Chemical Identity & Physical Properties
| Also known as | Selenium hydrideDihydrogen selenideSelenaneHydrogen selenide gas |
| CAS Number | 7783-07-5 |
| Appearance | Colorless gas with a highly offensive odor resembling decayed horseradish or rotten eggs at low concentrations. Odor fatigue occurs rapidly, deadening the sense of smell. |
| Flash Point | Not applicable (flammable gas) |
| Boiling Point | -41.3C (-42.3F) |
| Vapor Density | 2.8 (heavier than air) |
| Water Reactivity | Reacts with water to form selenious acid; not violent but toxic products formed |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2202
Extinguishing Media
Do not use water streams; dry chemical, CO2, or sand if applicable
PPE Requirements
⚠️ Level A required; full encapsulation with SCBA; extreme skin and inhalation hazard
Isolation & Evacuation
ERG 117: isolate 150m all directions initially; protect from heat and ignition sources; evacuate downwind areas immediately
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 117).
First Actions for a UN 2202 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.
- See Table 1 - Initial Isolation and Protective Action Distances.
Advertisement
📋 Copy & Share Field Card
UN 2202 — Hydrogen selenide, anhydrousHAZMAT RADIO NOTE — UN 2202
Product: Hydrogen selenide, anhydrous
Class 2 / Toxic Gas / ERG 117
PPE: Level A required; full encapsulation with SCBA; extreme skin and inhalation hazard
ISOLATION: ERG 117: isolate 150m all directions initially; protect from heat and ignition sources; evacuate downwind areas immediately
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 2202 — Hydrogen selenide, anhydrous
Class: 2 | Placard: Toxic Gas | ERG Guide: 117
Appearance: Colorless gas with a highly offensive odor resembling decayed horseradish or rotten eggs at low concentrations. Odor fatigue occurs rapidly, deadening the sense of smell.
Water Reactivity: Reacts with water to form selenious acid; not violent but toxic products formed
Extinguishing: Do not use water streams; dry chemical, CO2, or sand if applicable
PPE: Level A required; full encapsulation with SCBA; extreme skin and inhalation hazard
Isolation: ERG 117: isolate 150m all directions initially; protect from heat and ignition sources; evacuate downwind areas immediately
— Key Hazards —
• TOXIC; Extremely Hazardous.
• May be fatal if inhaled or absorbed through skin.
• Initial odor may be irritating or foul and may deaden your sense of smell.
— 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/2202 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN2202 Hydrogen selenide, anhydrous Cls2 ERG117 | allfirefighter.com/hazmat/un/2202SMS / 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/2202
Advertisement
Frequently Asked Questions about UN 2202
TOXIC; Extremely Hazardous. May be fatal if inhaled or absorbed through skin. Initial odor may be irritating or foul and may deaden your sense of smell. 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. These materials are extremely flammable. May form explosive mixtures with air.
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 required; full encapsulation with SCBA; extreme skin and inhalation hazard
Water reactivity: Reacts with water to form selenious acid; not violent but toxic products formed. Recommended extinguishing: Do not use water streams; dry chemical, CO2, or sand if applicable.
ERG Guide 117 recommendation: ERG 117: isolate 150m all directions initially; protect from heat and ignition sources; evacuate downwind areas immediately
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 117 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.