☣️ UN 3490 • CLASS 6
UN 3490 — Poisonous by inhalation liquid, water-reactive, flammable, n.o.s. (Inhalation Hazard Zone A)
Placard: Toxic. ERG Guide 155. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ Verification required:
Broad or variable material category; verify exact product, SDS and shipping papers.
⚠️ 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.
UN 3490 covers poisonous-by-inhalation liquid, n.o.s. in Inhalation Hazard Zone A, with additional water-reactive flammable hazards.
Hazard overview: The primary risk is severe inhalation toxicity. The liquid may also be flammable and corrosive, and vapors can collect in low or confined areas. Water contact may release flammable, toxic, or corrosive gases.
Response guidance: Isolate immediately, keep water away from the material, eliminate ignition sources, stay upwind, and use dry media or other SDS-approved agents only.
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UN 3490 Quick Details
UN 3490
Product name: Poisonous by inhalation liquid, water-reactive, flammable, n.o.s. (Inhalation Hazard Zone A)
DOT Class: 6
Placard type: Toxic
ERG Guide: 155 (check current ERG)
Initial isolation: ERG 155: Initial isolation 100m all directions; protect persons downwind; evacuate spill area immediately; Zone A inhalation hazard requires large-scale evacuation
Common Hazards of UN 3490
- HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
- Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
- Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
- Vapors may travel to source of ignition and flash back.
- Those substances designated with a (P) may polymerize explosively when heated or involved in a fire.
- Substance will react with water (some violently) releasing flammable, toxic or corrosive gases and runoff.
- Corrosives in contact with metals may evolve flammable hydrogen gas.
- Containers may explode when heated or if contaminated with water.
Chemical Identity & Physical Properties
The physical properties of UN 3490 vary by specific substance, but it is typically a liquid at room temperature with vapors heavier than air and may have a distinct chemical odor.
| Also known as | PIH liquid water-reactive flammableToxic inhalation hazard liquid (water-reactive, flammable)TIH Zone A water-reactive flammable liquidPoisonous liquid n.o.s. (water-reactive/flammable) |
| Appearance | Varies by specific substance; typically a liquid at room temperature with vapors heavier than air. May have distinct chemical odor depending on actual material. |
| Flash Point | Below 23C (73F) - highly flammable liquid |
| Boiling Point | Varies by specific substance - consult SDS for exact material |
| Vapor Density | Greater than 1 (heavier than air) - vapors accumulate in low areas |
| Water Reactivity | Reacts with water releasing flammable and/or toxic gases - avoid water contact |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3490
Extinguishing Media
Dry chemical, CO2, or dry sand recommended; avoid water-based agents due to reactivity
PPE Requirements
⚠️ Level A required for Zone A inhalation hazard; positive pressure SCBA mandatory; fully encapsulating chemical protective suit
Level A with fully encapsulating suit and SCBA is recommended because of the inhalation hazard.
Isolation & Evacuation
ERG 155: Initial isolation 100m all directions; protect persons downwind; evacuate spill area immediately; Zone A inhalation hazard requires large-scale evacuation
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 155).
First Actions for a UN 3490 Incident
- CALL 911. Then call the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate the spill or leak area in all directions using ERG guidance for the material and package size.
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials, increase the downwind precautionary distance as conditions require.
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📋 Copy & Share Field Card
UN 3490 — Poisonous by inhalation liquid, water-reHAZMAT RADIO NOTE — UN 3490
Product: Poisonous by inhalation liquid, water-reactive, flammable, n.o.s. (Inhalation Hazard Zone A)
Class 6 / Toxic / ERG 155
PPE: Level A required for Zone A inhalation hazard; positive pressure SCBA mandatory; fully encapsulating chemical protective suit
ISOLATION: ERG 155: Initial isolation 100m all directions; protect persons downwind; evacuate spill area immediately; Zone A inhalation hazard requires large-scale evacuation
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 3490 — Poisonous by inhalation liquid, water-reactive, flammable, n.o.s. (Inhalation Hazard Zone A)
Class: 6 | Placard: Toxic | ERG Guide: 155
Appearance: Varies by specific substance; typically a liquid at room temperature with vapors heavier than air. May have distinct chemical odor depending on actual material.
Water Reactivity: Reacts with water releasing flammable and/or toxic gases - avoid water contact
Extinguishing: Dry chemical, CO2, or dry sand recommended; avoid water-based agents due to reactivity
PPE: Level A required for Zone A inhalation hazard; positive pressure SCBA mandatory; fully encapsulating chemical protective suit
Isolation: ERG 155: Initial isolation 100m all directions; protect persons downwind; evacuate spill area immediately; Zone A inhalation hazard requires large-scale evacuation
— Key Hazards —
• HIGHLY FLAMMABLE: Will be easily ignited by heat, sparks or flames.
• Vapors form explosive mixtures with air: indoors, outdoors and sewers explosion hazards.
• Most vapors are heavier than air. They will spread along the ground and collect in low or confined areas
— First Actions —
• CALL 911. Then call the emergency response number on the shipping paper, if available.
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/poisonous-by-inhalation-liquid-un-3490 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN3490 Poisonous by inhalation liquid, water-reactive, flammable, n.o.s. (Inhalation Hazard Zone A) Cls6 ERG155 | allfirefighter.com/hazmat/un/poisonous-by-inhalation-liquid-un-3490SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/poisonous-by-inhalation-liquid-un-3490
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Frequently Asked Questions about UN 3490
Yes. It has flammable liquid hazards in addition to inhalation toxicity.
Yes. Water contact may release flammable, toxic, or corrosive gases and may intensify the incident.
Level A with fully encapsulating suit and SCBA is recommended because of the inhalation hazard.
Treat as an extreme inhalation hazard, isolate the area, stay upwind, and evacuate downwind as directed by ERG and incident command.
UN 3490 is assigned to ERG Guide 155 for initial emergency response guidance.
Inhalation Hazard Zone A indicates a severe toxic inhalation risk; Zone A is more severe than Zone B.
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.