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 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.