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.
UN 2789 At a Glance
UN 2789 (Acetic acid, solution, more than 80% acid) is listed as DOT Class 8 Corrosive and is assigned to ERG Guide 132. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.
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.