☣️ UN 1873 • CLASS 5
Perchloric acid, with more than 50% but not more than 72% acid
Placard: Oxidizer. 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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Quick details
UN 1873
Class: 5
Placard type: Oxidizer
ERG: Guide 143 (check current ERG)
Isolation: ERG 143: isolate spill 25-50m; initial evacuation 800m downwind if tank/railcar fire
Chemical & Response Details
| Also known as | Perchloric acidChloric acid, per-Hyperchloric acidDioxonium perchlorate |
| CAS Number | 7601-90-3 |
| Appearance | Colorless to slightly yellow, fuming liquid with a sharp, acrid odor. Highly corrosive and oxidizing at room temperature. |
| Flash Point | Not applicable (strong oxidizer, not flammable itself) |
| Boiling Point | 203C (397F) at 70% concentration, decomposes |
| Vapor Density | 3.5 (heavier than air) |
| Water Reactivity | Miscible with water, generates heat on dilution; dilution reduces explosive hazard |
| Extinguishing | Do not use foam or water streams; use large volumes of water flooding from distance only |
| PPE | ⚠️ Level A required; full encapsulation, SCBA, acid-resistant materials; no contact with organics |
| Isolation | ERG 143: isolate spill 25-50m; initial evacuation 800m downwind if tank/railcar fire |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- May explode from friction, heat or contamination.
- These substances will accelerate burning when involved in a fire.
- May ignite combustibles (wood, paper, oil, clothing, etc.).
- Some will react explosively with hydrocarbons (fuels).
- Containers may explode when heated.
- Runoff may create fire or explosion hazard.
- TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe
- Fire may produce irritating and/or toxic gases.
First actions (field-minded)
- 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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UN 1873 — Perchloric acid, with more than 50% but HAZMAT RADIO NOTE — UN 1873
Product: Perchloric acid, with more than 50% but not more than 72% acid
Class 5 / Oxidizer / ERG 143
PPE: Level A required; full encapsulation, SCBA, acid-resistant materials; no contact with organics
ISOLATION: ERG 143: isolate spill 25-50m; initial evacuation 800m downwind if tank/railcar 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 1873 — Perchloric acid, with more than 50% but not more than 72% acid
Class: 5 | Placard: Oxidizer | ERG Guide: 143
Appearance: Colorless to slightly yellow, fuming liquid with a sharp, acrid odor. Highly corrosive and oxidizing at room temperature.
Water Reactivity: Miscible with water, generates heat on dilution; dilution reduces explosive hazard
Extinguishing: Do not use foam or water streams; use large volumes of water flooding from distance only
PPE: Level A required; full encapsulation, SCBA, acid-resistant materials; no contact with organics
Isolation: ERG 143: isolate spill 25-50m; initial evacuation 800m downwind if tank/railcar fire
— Key Hazards —
• May explode from friction, heat or contamination.
• These substances will accelerate burning when involved in a fire.
• May ignite combustibles (wood, paper, oil, clothing, etc.).
— 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/1873 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1873 Perchloric acid, with more than 50% but not more than 72% acid Cls5 ERG143 | allfirefighter.com/hazmat/un/1873SMS / 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/1873
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FAQ
May explode from friction, heat or contamination. These substances will accelerate burning when involved in a fire. May ignite combustibles (wood, paper, oil, clothing, etc.). Some will react explosively with hydrocarbons (fuels). Containers may explode when heated. Runoff may create fire or explosion hazard. TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe Fire may produce irritating and/or toxic gases.
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 required; full encapsulation, SCBA, acid-resistant materials; no contact with organics
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 143 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.