UN 3474 — Hydroxybenzotriazole, monohydrate
Placard: Flammable Solid. ERG Guide 113. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3474 is Hydroxybenzotriazole, monohydrate, a self-reactive/flammable solid assigned to ERG Guide 113. Moisture/stabilizer condition and decomposition risk must be verified.
Hazard overview: Self-reactive/flammable solid; heat, friction, shock or contamination can cause hazardous decomposition. Dry material may be more energetic than wetted or stabilized material. Dust may irritate eyes and respiratory tract and can spread contamination.
Response guidance: For UN 3474, isolate the area, avoid skin contact and use SCBA where vapor, dust, mist or fire is present. Contain runoff and verify controls with SDS/ERG 113.
Firefighter training notes: Training for UN 3474 should emphasize exposure routes, SCBA use, vapor/dust monitoring, decontamination, runoff containment and SDS verification. Use ERG 113, SDS and local SOP.
Regulatory context: Hydroxybenzotriazole, monohydrate is regulated as a hazardous material for transport and emergency response. Storage, reporting, exposure, waste and incident-notification duties depend on quantity, concentration, formulation and jurisdiction; verify shipping papers, SDS and authority guidance.
Storage & handling: Hydroxybenzotriazole, monohydrate should be stored in approved compatible packaging, protected from heat, friction, shock, contamination and drying or moisture changes outside SDS limits.
UN 3474 Quick Details
Common Hazards of UN 3474
- Self-reactive/flammable solid; heat, friction, shock or contamination can cause hazardous decomposition.
- Dry material may be more energetic than wetted or stabilized material.
- Dust may irritate eyes and respiratory tract and can spread contamination.
- May burn rapidly if heated or involved in fire.
- Fire may produce nitrogen oxides, carbon monoxide and irritating/toxic smoke.
- Runoff or debris may carry reactive residue.
- Exact hydration, moisture content and stabilizer condition must be verified from SDS.
Chemical Identity & Physical Properties
White to off-white crystalline solid or powder. Odorless or faint characteristic odor. Hygroscopic material that forms monohydrate crystals at room temperature.
| Also known as | HOBt monohydrateHydroxy-benzotriazole monohydrateHydroxybenzotriazole hydrateHOBt·H2O |
| CAS Number | 123333-53-9 |
| Appearance | White to off-white crystalline solid or powder. Odorless or faint characteristic odor. Hygroscopic material that forms monohydrate crystals at room temperature. |
| Flash Point | Not applicable when hydrated; dried material is shock-sensitive and explosive |
| Boiling Point | Decomposes before boiling at approximately 157-160C (315-320F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Soluble in water; no violent reaction but dissolution releases heat |
Fireground Response Guidance — UN 3474
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for dust, smoke or fire. Wear full protective clothing and avoid friction, heat, contamination and direct contact.
Isolation & Evacuation
First Actions for a UN 3474 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.
- Avoid heat, friction, shock, contamination and incompatible extinguishing media.
- Do not touch damaged containers, equipment or spilled material without proper training and PPE.
- Prevent contaminated liquid, dust, runoff and decontamination waste from spreading.
- Ventilate confined spaces only after monitoring and only if properly trained and equipped.
- Use ERG Guide 113, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 3474 — Hydroxybenzotriazole, monohydrateUse 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.