☣️ UN 1798 • CLASS 8
UN 1798 — Nitrohydrochloric acid
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 1798 Quick Details
UN 1798
Product name: Nitrohydrochloric acid
DOT Class: 8
Placard type: Corrosive
ERG Guide: 157 (check current ERG)
Initial isolation: ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwind if large spill or fire
Common Hazards of UN 1798
- 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 | Aqua regiaNitro-muriatic acidChloronitrous acidNitromuriatic acidNitro-hydrochloric acid |
| Appearance | Yellow to reddish-brown fuming liquid with a pungent, choking odor. Highly corrosive mixture of concentrated nitric and hydrochloric acids. |
| Flash Point | Not applicable (non-flammable corrosive liquid) |
| Boiling Point | Variable depending on composition, typically 108-121C (226-250F) |
| Vapor Density | Greater than 1 (heavier than air) |
| Water Reactivity | Reacts exothermically with water generating heat and toxic fumes of nitrogen oxides and hydrogen chloride |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 1798
Extinguishing Media
Do not use water directly on liquid; use water spray to reduce vapors; dry chemical or CO2 for small fires
PPE Requirements
⚠️ Level A or B required; full-face SCBA; acid-resistant suit, gloves, and boots mandatory
Isolation & Evacuation
ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwind if large spill or fire
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 157).
First Actions for a UN 1798 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 1798 — Nitrohydrochloric acidHAZMAT RADIO NOTE — UN 1798
Product: Nitrohydrochloric acid
Class 8 / Corrosive / ERG 157
PPE: Level A or B required; full-face SCBA; acid-resistant suit, gloves, and boots mandatory
ISOLATION: ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwind if large spill or fire
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 1798 — Nitrohydrochloric acid
Class: 8 | Placard: Corrosive | ERG Guide: 157
Appearance: Yellow to reddish-brown fuming liquid with a pungent, choking odor. Highly corrosive mixture of concentrated nitric and hydrochloric acids.
Water Reactivity: Reacts exothermically with water generating heat and toxic fumes of nitrogen oxides and hydrogen chloride
Extinguishing: Do not use water directly on liquid; use water spray to reduce vapors; dry chemical or CO2 for small fires
PPE: Level A or B required; full-face SCBA; acid-resistant suit, gloves, and boots mandatory
Isolation: ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwind if large spill or fire
— 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/1798 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1798 Nitrohydrochloric acid Cls8 ERG157 | ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwin | allfirefighter.com/hazmat/un/1798SMS / 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/1798
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Frequently Asked Questions about UN 1798
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; acid-resistant suit, gloves, and boots mandatory
Water reactivity: Reacts exothermically with water generating heat and toxic fumes of nitrogen oxides and hydrogen chloride. Recommended extinguishing: Do not use water directly on liquid; use water spray to reduce vapors; dry chemical or CO2 for small fires.
ERG Guide 157 recommendation: ERG 157: isolate spill area minimum 25m in all directions; evacuate 800m downwind if large spill or fire
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.