UN 1790 — Hydrofluoric acid
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1790 is Hydrofluoric acid, a Class 8 corrosive liquid assigned to ERG Guide 157. It is a highly toxic and corrosive hydrogen fluoride solution that can cause severe chemical burns, respiratory injury and systemic toxicity.
Hazard overview: UN 1790 is one of the more dangerous corrosive acid entries because hydrofluoric acid can penetrate skin and damage deep tissue, sometimes with delayed symptoms. Vapors and mist can injure the eyes and respiratory tract, while contact with metals may release flammable hydrogen gas. Heating, fire or dilution can increase corrosive vapor production and create toxic runoff hazards.
Response guidance: For a UN 1790 incident, responders should confirm concentration and product identity using shipping papers, container markings, SDS and ERG Guide 157. Establish incident command, isolate the area, keep crews upwind and uphill, avoid vapor or liquid contact, control ignition sources where hydrogen may be present, and request hazmat and medical support for any suspected HF exposure under local SOP.
Firefighter training notes: Training should emphasize HF exposure, PPE compatibility, isolation, decontamination and medical coordination using ERG 157, SDS and local SOP.
Regulatory context: Hydrofluoric acid is regulated as a hazardous material; verify requirements through shipping papers, SDS and applicable authorities.
Storage & handling: Hydrofluoric acid should be stored in compatible acid-resistant containers according to SDS and local hazmat procedures.
UN 1790 Quick Details
Common Hazards of UN 1790
- TOXIC and/or CORROSIVE; inhalation, ingestion or skin and eye contact with vapors, liquid or mist may cause severe injury or death.
- Hydrofluoric acid can penetrate skin and cause deep tissue injury that may be delayed and life-threatening.
- Vapors are highly irritating and corrosive to the eyes, skin and respiratory tract.
- Contact with metals may generate flammable hydrogen gas.
- Reaction with water or moisture may generate heat and increase fuming.
- Fire may produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and may cause environmental contamination.
- Vapors may accumulate in confined or low areas such as basements, tanks and enclosed spaces.
Chemical Identity & Physical Properties
Hydrofluoric acid is typically a colorless to slightly colored fuming liquid with a sharp, irritating odor. It is miscible with water, fumes in moist air and can attack glass, metals and many materials depending on concentration.
| Also known as | Hydrogen fluoride solutionHydrofluoric acid solutionHF acidFluorhydric acidFluoric acid |
| CAS Number | 7664-39-3 |
| Appearance | Colorless to slightly colored fuming liquid with a pungent, irritating odor. Highly corrosive and fumes strongly in moist air. |
| Flash Point | Not applicable (aqueous solution) |
| Boiling Point | 106-120C (223-248F) depending on concentration |
| Vapor Density | 1.27 (heavier than air) |
| Water Reactivity | Miscible with water; dilution generates heat and increases fuming |
Fireground Response Guidance — UN 1790
Extinguishing Media
PPE Requirements
Responders should use positive-pressure SCBA and acid-resistant chemical protective clothing for potential exposure to hydrofluoric acid vapor, mist or liquid. Entry PPE may require Level A protection, with glove and suit compatibility confirmed by SDS, incident command, air monitoring and local hazmat SOP.
Isolation & Evacuation
First Actions for a UN 1790 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, mist or fumes.
- Do not touch damaged containers or spilled material unless properly trained and wearing appropriate protective equipment.
- Avoid all skin and eye contact; hydrofluoric acid exposure requires immediate medical evaluation under local protocols.
- Ventilate closed spaces before entering, but only if properly trained, equipped and authorized by incident command.
- Isolate the spill or leak area in all directions for at least 50 meters (150 feet) for liquids.
- For highlighted materials, consult ERG Table 1 for Initial Isolation and Protective Action Distances.
- For non-highlighted materials, increase the immediate precautionary distance as needed in the downwind direction based on conditions.
📋 Copy & Share Field Card
UN 1790 — Hydrofluoric acidUse 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.