UN 2438 — Trimethylacetyl chloride
Placard: Toxic. ERG Guide 131. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2438 is Trimethylacetyl chloride, a toxic corrosive acid chloride assigned to ERG Guide 131. Water or moist air can release hydrogen chloride fumes and heat.
Hazard overview: TOXIC and CORROSIVE acid chloride; inhalation or skin contact may cause severe injury. Reacts with water or moist air, releasing hydrogen chloride fumes and heat. Combustible or flammable behavior depends on the specific acid chloride.
Response guidance: For UN 2438, isolate the spill, stay upwind and use SCBA with chemical protection. Control moisture contact, contain acidic runoff and use dry compatible agents under SDS and ERG 131 guidance.
Firefighter training notes: Training for UN 2438 should emphasize water-reactive corrosive fuming, HCl hazards, dry-agent selection, Level A/B decisions, decontamination and acidic runoff control. Use ERG 131, SDS and local SOP.
Regulatory context: Trimethylacetyl chloride is regulated as a hazardous material for transport and emergency response. Storage, exposure, spill reporting, waste and fire-code duties depend on quantity, concentration and jurisdiction; verify shipping papers, SDS and local authority requirements.
Storage & handling: Trimethylacetyl chloride should be stored dry in tightly closed compatible containers away from water, moisture, bases, oxidizers/reducing agents where incompatible, heat and unauthorized access. Provide secondary containment.
UN 2438 Quick Details
Common Hazards of UN 2438
- TOXIC and CORROSIVE acid chloride; inhalation or skin contact may cause severe injury.
- Reacts with water or moist air, releasing hydrogen chloride fumes and heat.
- Combustible or flammable behavior depends on the specific acid chloride.
- Vapors may collect in low or confined areas and irritate eyes, skin and respiratory tissue.
- Fire may produce hydrogen chloride, phosgene-type gases and other toxic/corrosive smoke.
- Runoff may be acidic, corrosive and toxic.
- Containers may rupture when heated or contaminated with water.
Chemical Identity & Physical Properties
Colorless to pale yellow liquid with a pungent, acrid odor. Fumes in moist air.
| Also known as | Pivaloyl chloride2,2-Dimethylpropanoyl chloridePivalyl chloridetert-Butylcarbonyl chloride |
| CAS Number | 3282-30-2 |
| Appearance | Colorless to pale yellow liquid with a pungent, acrid odor. Fumes in moist air. |
| Flash Point | 51°C (124°F) |
| Boiling Point | 105-106°C (221-223°F) |
| Vapor Density | 4.2 (heavier than air) |
| Water Reactivity | Reacts violently with water, releasing HCl gas and heat. Do not use water directly on material. |
Fireground Response Guidance — UN 2438
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical-resistant protective clothing. Level A may be needed for heavy vapor, fuming, splash risk or unknown concentrations.
Isolation & Evacuation
First Actions for a UN 2438 Incident
- Call 911 and the emergency response number on the shipping paper, if available.
- Keep unauthorized personnel away and establish incident command.
- Stay upwind, uphill and upstream.
- Avoid breathing vapor, dust, mist, smoke or fumes and avoid skin or eye contact.
- Keep water contact controlled because moisture can increase heat release, corrosive fuming or ignition.
- Do not touch damaged containers or spilled material without proper training and PPE.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 131, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 2438 — Trimethylacetyl chlorideUse 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.