UN 1835 — Tetramethylammonium hydroxide aqueous solution with more than 2.5% but less than 25% tetramethylammonium hydroxide
Placard: Corrosive. ERG Guide 153. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1835 is Tetramethylammonium hydroxide aqueous solution with more than 2.5% but less than 25% tetramethylammonium hydroxide, a toxic corrosive alkaline solution assigned to ERG Guide 153. Skin exposure can cause both chemical burns and serious systemic tetramethylammonium toxicity.
Hazard overview: UN 1835 presents corrosive alkaline burn, dermal toxicity, ingestion and contaminated-runoff hazards. Prevent all skin contact and control decontamination water.
Response guidance: For a UN 1835 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 153. Establish incident command, isolate the area, stay upwind, prevent incompatible contact, control runoff and choose entry or fire-control actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1835 should emphasize caustic burns, heat from dilution or moisture reaction, dust/mist control, PPE selection and alkaline runoff containment. Use ERG 153, SDS and local SOP.
Regulatory context: Tetramethylammonium hydroxide aqueous solution with more than 2.5% but less than 25% tetramethylammonium hydroxide is regulated as a hazardous material for transportation and emergency response purposes. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by concentration, formulation, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Tetramethylammonium hydroxide aqueous solution with more than 2.5% but less than 25% tetramethylammonium hydroxide should be stored in compatible corrosion-resistant containers with secondary containment, away from acids, reactive metals where incompatible, oxidizers where incompatible and unauthorized access. Keep containers closed and protected from heat or freezing as directed by SDS.
UN 1835 Quick Details
Common Hazards of UN 1835
- TOXIC and CORROSIVE tetramethylammonium hydroxide solution; skin contact, ingestion or inhalation may cause severe injury.
- Strong alkaline liquid can cause deep chemical burns to eyes and skin.
- Tetramethylammonium ion can produce serious systemic toxicity, so skin exposure should be treated as significant.
- Aqueous solution is not normally flammable, but fire may produce irritating/toxic gases.
- Runoff may be strongly alkaline and toxic.
- Containers may rupture or fail when heated.
- Avoid all skin contact and prevent contaminated clothing exposure.
Chemical Identity & Physical Properties
Clear to slightly yellow liquid with an ammonia-like or fishy odor. Strong alkaline solution that is highly corrosive and toxic.
| Also known as | TMAHTetramethylammonium hydroxide solutionHydroxide de tetramethylammoniumTetramethylammonium hydroxide pentahydrate |
| CAS Number | 75-59-2 |
| Appearance | Clear to slightly yellow liquid with an ammonia-like or fishy odor. Strong alkaline solution that is highly corrosive and toxic. |
| Flash Point | Not applicable (aqueous solution, non-flammable) |
| Boiling Point | Approximately 100C (212F), varies with concentration |
| Vapor Density | Not applicable (aqueous solution) |
| Water Reactivity | Miscible with water; generates heat when diluted but does not react violently |
Fireground Response Guidance — UN 1835
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for mist, vapor, fire or confined-space exposure. Wear chemical-resistant clothing, face/eye protection, boots and gloves selected from SDS; prevent all skin contact because systemic toxicity is possible.
Isolation & Evacuation
First Actions for a UN 1835 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, fumes, dust, mist or spray and avoid skin or eye contact.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Avoid creating splashes or mist and prevent alkaline/corrosive runoff from entering drains.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or leak area and expand the perimeter if vapor, dust, fire involvement, water reaction or unknown concentration is present.
- Use ERG Guide 153, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1835 — Tetramethylammonium hydroxide aqueous soUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.