☣️ UN 3456 • CLASS 8
UN 3456 — Nitrosylsulphuric acid, solid
Placard: Corrosive. ERG Guide 157. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
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⚠️ This page is a quick-reference aid. For real incidents: stage upwind, isolate, deny entry, request Hazmat early, and consult the current ERG + SOP/SOG.
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UN 3456 Quick Details
UN 3456
Product name: Nitrosylsulphuric acid, solid
DOT Class: 8
Placard type: Corrosive
ERG Guide: 157 (check current ERG)
Initial isolation: ERG 157: Initial isolate 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation for 1600m downwind
Common Hazards of UN 3456
- TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
- Reaction with water or moist air may release toxic, corrosive or flammable gases.
- Reaction with water may generate much heat that will increase the concentration of fumes in the air.
- Fire will produce irritating, corrosive and/or toxic gases.
- Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental
- Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive
- UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above
- Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
Chemical Identity & Physical Properties
| 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 |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3456
Extinguishing Media
Dry chemical, soda ash, lime, sand; avoid water-based agents due to violent reaction
PPE Requirements
⚠️ Level A or B required; full-face SCBA, chemical-resistant suit, boots, and gloves; extreme corrosive and toxic vapor hazard
Isolation & Evacuation
ERG 157: Initial isolate 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation for 1600m downwind
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 157).
First Actions for a UN 3456 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Ventilate closed spaces before entering, but only if properly trained and equipped.
- Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
- For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.
- For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind
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📋 Copy & Share Field Card
UN 3456 — Nitrosylsulphuric acid, solidHAZMAT RADIO NOTE — UN 3456
Product: Nitrosylsulphuric acid, solid
Class 8 / Corrosive / ERG 157
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, boots, and gloves; extreme corrosive and toxic vapor hazard
ISOLATION: ERG 157: Initial isolate 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation for 1600m downwind
ACTION: Stage upwind · Isolate · Deny entry · Request HazmatRADIO
Use for: Quick radio or face-to-face size-up. Short, structured, field-ready.
=== IC HAZMAT BRIEFING ===
UN 3456 — Nitrosylsulphuric acid, solid
Class: 8 | Placard: Corrosive | ERG Guide: 157
Appearance: White to yellowish crystalline solid with a pungent, irritating odor. Hygroscopic and fumes in moist air.
Water Reactivity: Reacts vigorously with water, releasing heat and toxic/corrosive fumes including nitric acid and sulfuric acid vapors
Extinguishing: Dry chemical, soda ash, lime, sand; avoid water-based agents due to violent reaction
PPE: Level A or B required; full-face SCBA, chemical-resistant suit, boots, and gloves; extreme corrosive and toxic vapor hazard
Isolation: ERG 157: Initial isolate 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation for 1600m downwind
— Key Hazards —
• TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance
• Reaction with water or moist air may release toxic, corrosive or flammable gases.
• Reaction with water may generate much heat that will increase the concentration of fumes in the air.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Keep unauthorized personnel away.
• Stay upwind, uphill and/or upstream.
• Ventilate closed spaces before entering, but only if properly trained and equipped.
SOURCE: allfirefighter.com/hazmat/un/3456 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3456 Nitrosylsulphuric acid, solid Cls8 ERG157 | allfirefighter.com/hazmat/un/3456SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS. Includes link to full page.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/3456
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Frequently Asked Questions about UN 3456
TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance Reaction with water or moist air may release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.).
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Keep unauthorized personnel away. Stay upwind, uphill and/or upstream.
Level A or B required; full-face SCBA, chemical-resistant suit, boots, and gloves; extreme corrosive and toxic vapor hazard
Water reactivity: Reacts vigorously with water, releasing heat and toxic/corrosive fumes including nitric acid and sulfuric acid vapors. Recommended extinguishing: Dry chemical, soda ash, lime, sand; avoid water-based agents due to violent reaction.
ERG Guide 157 recommendation: ERG 157: Initial isolate 100m in all directions; if tank/rail car involved in fire, isolate 800m and consider evacuation for 1600m downwind
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 157 and your department SOP/SOG for incident-specific protective actions.
Sources (high level): DOT/PHMSA marking & class concepts + ERG usage principles.
This page does not reproduce ERG guide text—always consult the current ERG for incident-specific protective actions.