UN 2789 — Acetic acid, solution, more than 80% acid
Placard: Corrosive. ERG Guide 132. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
Acetic acid solution, more than 80% acid is a concentrated corrosive acid that may also present a combustible vapor hazard. Treat vapors, liquid contact and runoff as hazardous.
Hazard overview: Concentrated acetic acid solution is corrosive to skin, eyes and respiratory tissue. Vapors are irritating and heavier than air; they can collect in low or poorly ventilated spaces. Solutions over 80% acid can be combustible and vapors may ignite when heated.
Response guidance: Isolate the area, eliminate ignition sources and keep responders upwind. Use SCBA, acid-resistant PPE and compatible absorbent; cool exposed containers from a distance.
Firefighter training notes: Train responders to identify the UN number, product name, placard, container type and exposure route before committing personnel to the hot zone.
Regulatory context: Use the proper DOT shipping description, ERG guide, SDS and site-specific response plan; do not substitute this summary for regulatory compliance.
Storage & handling: Store in corrosion-resistant containers away from oxidizers, bases, metals, ignition sources and incompatible organic materials.
UN 2789 Quick Details
Common Hazards of UN 2789
- Concentrated acetic acid solution is corrosive to skin, eyes and respiratory tissue.
- Vapors are irritating and heavier than air; they can collect in low or poorly ventilated spaces.
- Solutions over 80% acid can be combustible and vapors may ignite when heated.
- Vapors may travel to ignition sources and flash back under fire conditions.
- Contact with metals may release flammable hydrogen gas.
- Mixing with water can generate heat and splattering if done improperly.
- Fire may produce irritating acidic vapors and container rupture risk.
- Runoff can be corrosive and harmful to waterways.
Chemical Identity & Physical Properties
Clear, colorless liquid with a pungent, vinegar-like odor. Corrosive and miscible with water.
| Also known as | Glacial acetic acidEthanoic acidVinegar acidMethanecarboxylic acid |
| CAS Number | 64-19-7 |
| Appearance | Clear, colorless liquid with a pungent, vinegar-like odor. Corrosive and miscible with water. |
| Flash Point | 39°C (103°F) |
| Boiling Point | 118°C (244°F) |
| Vapor Density | 2.1 (heavier than air) |
| Water Reactivity | Miscible with water; dilution can generate heat and splatter. Add acid to water only under controlled specialist direction. |
Fireground Response Guidance — UN 2789
Extinguishing Media
PPE Requirements
Level B minimum; SCBA and chemical-resistant suit required due to corrosive vapors
Isolation & Evacuation
First Actions for a UN 2789 Incident
- Call 911 and the emergency response number shown on the shipping papers.
- Keep unauthorized personnel away and establish an initial isolation perimeter.
- Stay upwind, uphill and upstream; avoid low areas where vapors or runoff may collect.
- Avoid breathing vapors, dust, mist or smoke and prevent skin and eye contact.
- Do not touch damaged packages, leaking containers or spilled material without appropriate PPE.
- Eliminate ignition sources; stop traffic, engines, smoking and open flames if it can be done safely.
- Ventilate confined spaces only when responders are trained, equipped and monitoring conditions.
- Use ERG, SDS, shipping papers and air monitoring to set final isolation, evacuation and decon actions.
📋 Copy & Share Field Card
UN 2789 — Acetic acid, solution, more than 80% aciUse 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.