UN 3456 — Nitrosylsulphuric acid, solid
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 3456 At a Glance
UN 3456 (Nitrosylsulphuric acid, solid) is listed as DOT Class 8 Corrosive and is assigned to ERG Guide 157. Use this page to review placard data, common hazards, PPE notes, isolation context, first actions, and related UN numbers.
UN 3456 is Nitrosylsulphuric acid, solid, a toxic corrosive moisture-reactive acid solid assigned to ERG Guide 157. Water releases heat and acid/NOx/SOx fumes.
Hazard overview: TOXIC and CORROSIVE acidic solid; dust, fumes or contact can severely burn tissue. Reacts vigorously with water or moist air, releasing heat and nitrogen/sulfur oxides or acidic fumes. Hygroscopic material may fume in moist air and contaminate tools, PPE and runoff.
Response guidance: For UN 3456, isolate the spill, avoid fuming dust/mist and use SCBA with acid/fluoride protection. Control water reaction and runoff under ERG 157.
Firefighter training notes: Training for UN 3456 should emphasize exposure routes, SCBA use, vapor/dust monitoring, decontamination, runoff containment and SDS verification. Use ERG 157, SDS and local SOP.
Regulatory context: Nitrosylsulphuric acid, solid 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: Nitrosylsulphuric acid, solid should be stored in tightly closed compatible containers with ventilation, secondary containment, restricted access and SDS-based segregation from incompatible materials.
UN 3456 Quick Details
Common Hazards of UN 3456
- TOXIC and CORROSIVE acidic solid; dust, fumes or contact can severely burn tissue.
- Reacts vigorously with water or moist air, releasing heat and nitrogen/sulfur oxides or acidic fumes.
- Hygroscopic material may fume in moist air and contaminate tools, PPE and runoff.
- Non-combustible, but heating decomposes it to toxic/corrosive gases.
- Contact with metals may generate flammable hydrogen under acidic conditions.
- Runoff may be strongly acidic, corrosive and toxic.
- Avoid direct water contact with bulk material unless directed by qualified incident command.
Chemical Identity & Physical Properties
White to yellowish crystalline solid with a pungent, irritating odor. Hygroscopic and fumes in moist air.
| Also known as | Nitrosylsulfuric acidNitrosyl hydrogen sulfateNitrosyl bisulfateNOHSO4Lead chamber crystals |
| CAS Number | 7782-78-7 |
| Appearance | White to yellowish crystalline solid with a pungent, irritating odor. Hygroscopic and fumes in moist air. |
| Flash Point | Not applicable (non-flammable solid) |
| Boiling Point | Decomposes before boiling, releasing toxic nitrogen oxides and sulfur oxides |
| Vapor Density | Not applicable (solid, but releases heavy vapors upon decomposition or contact with moisture) |
| Water Reactivity | Reacts vigorously with water, releasing heat and toxic/corrosive fumes including nitric acid and sulfuric acid vapors |
Fireground Response Guidance — UN 3456
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and acid/fluoride-resistant chemical protective clothing. Level A may be needed for fuming, splash or unknown concentration.
Isolation & Evacuation
First Actions for a UN 3456 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, acids/bases or incompatible materials controlled until product-specific guidance is confirmed.
- 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 157, SDS, shipping papers and monitoring to set isolation, evacuation and entry decisions.
📋 Copy & Share Field Card
UN 3456 — Nitrosylsulphuric acid, solidUse 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.