☣️ UN 3423 • CLASS 8
UN 3423 — Tetramethylammonium hydroxide, solid
Placard: Corrosive. ERG Guide 153. 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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UN 3423 Quick Details
UN 3423
Product name: Tetramethylammonium hydroxide, solid
DOT Class: 8
Placard type: Corrosive
ERG Guide: 153 (check current ERG)
Initial isolation: ERG 153: isolate spill/leak area immediately for at least 25-50m in all directions; if tank/rail car involved in fire, isolate 800m in all directions
Common Hazards of UN 3423
- TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
- Methyl bromoacetate (UN2643) is an eye irritant/lachrymator (causes flow of tears).
- Contact with molten substance may cause severe burns to skin and eyes.
- Avoid any skin contact.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Combustible material: may burn but does not ignite readily.
- When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion
Chemical Identity & Physical Properties
| Also known as | TMAHTetramethylammonium hydroxideHydroxide de tetramethylammoniumTMAOHTetramethyl ammonium hydroxide |
| CAS Number | 75-59-2 |
| Appearance | White to off-white crystalline solid or pellets at room temperature. Hygroscopic material with no distinct odor or faint amine-like odor when exposed to moisture. |
| Flash Point | Not applicable (solid) |
| Boiling Point | 130C (266F) with decomposition |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Dissolves readily in water, generating heat; highly alkaline solution (pH >14) |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3423
Extinguishing Media
Dry chemical, CO2, or dry sand; water spray may be used to cool containers but avoid direct contact with solid
PPE Requirements
⚠️ Level B minimum; SCBA required; full face shield, chemical-resistant suit, neoprene or butyl rubber gloves; extreme corrosive hazard to skin and eyes
Isolation & Evacuation
ERG 153: isolate spill/leak area immediately for at least 25-50m in all directions; if tank/rail car involved in fire, isolate 800m in all directions
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 153).
First Actions for a UN 3423 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.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- 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 3423 — Tetramethylammonium hydroxide, solidHAZMAT RADIO NOTE — UN 3423
Product: Tetramethylammonium hydroxide, solid
Class 8 / Corrosive / ERG 153
PPE: Level B minimum; SCBA required; full face shield, chemical-resistant suit, neoprene or butyl rubber gloves; extreme corrosive hazard to skin and eyes
ISOLATION: ERG 153: isolate spill/leak area immediately for at least 25-50m in all directions; if tank/rail car involved in fire, isolate 800m in all directions
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 3423 — Tetramethylammonium hydroxide, solid
Class: 8 | Placard: Corrosive | ERG Guide: 153
Appearance: White to off-white crystalline solid or pellets at room temperature. Hygroscopic material with no distinct odor or faint amine-like odor when exposed to moisture.
Water Reactivity: Dissolves readily in water, generating heat; highly alkaline solution (pH >14)
Extinguishing: Dry chemical, CO2, or dry sand; water spray may be used to cool containers but avoid direct contact with solid
PPE: Level B minimum; SCBA required; full face shield, chemical-resistant suit, neoprene or butyl rubber gloves; extreme corrosive hazard to skin and eyes
Isolation: ERG 153: isolate spill/leak area immediately for at least 25-50m in all directions; if tank/rail car involved in fire, isolate 800m in all directions
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury
• Methyl bromoacetate (UN2643) is an eye irritant/lachrymator (causes flow of tears).
• Contact with molten substance may cause severe burns to skin and eyes.
— 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.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/3423 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3423 Tetramethylammonium hydroxide, solid Cls8 ERG153 | allfirefighter.com/hazmat/un/3423SMS / 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/3423
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Frequently Asked Questions about UN 3423
TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury Methyl bromoacetate (UN2643) is an eye irritant/lachrymator (causes flow of tears). Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Combustible material: may burn but does not ignite readily. When heated, vapors may form explosive mixtures with air: indoors, outdoors and sewers explosion
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 B minimum; SCBA required; full face shield, chemical-resistant suit, neoprene or butyl rubber gloves; extreme corrosive hazard to skin and eyes
Water reactivity: Dissolves readily in water, generating heat; highly alkaline solution (pH >14). Recommended extinguishing: Dry chemical, CO2, or dry sand; water spray may be used to cool containers but avoid direct contact with solid.
ERG Guide 153 recommendation: ERG 153: isolate spill/leak area immediately for at least 25-50m in all directions; if tank/rail car involved in fire, isolate 800m in all directions
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 153 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.