☣️ UN 2798 • CLASS 8
UN 2798 — Benzene phosphorus dichloride
Placard: Corrosive. ERG Guide 137. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
🚒☣️
⚠️ 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.
Benzene phosphorus dichloride is a corrosive organophosphorus chloride that fumes in moist air. Moisture contact can release hydrogen chloride fumes and heat.
Hazard overview: This material presents both corrosive vapor and liquid-contact hazards. Water, humidity or wet firefighting runoff can intensify fuming and make the release more difficult to control.
Response guidance: Keep responders upwind, isolate the area and avoid water contact with the product. Use dry chemical, carbon dioxide or dry sand for small fires or spill control, and cool exposed containers from a safe distance only if water will not contact the material.
Advertisement
UN 2798 Quick Details
UN 2798
Product name: Benzene phosphorus dichloride
DOT Class: 8
Placard type: Corrosive
ERG Guide: 137 (check current ERG)
Initial isolation: ERG 137: Initial isolation 50m in all directions; Protective Action Distance 0.1 km (day) / 0.3 km (night) for spills; evacuate immediate area if fire involved
Common Hazards of UN 2798
- Liquid and vapors are corrosive and toxic to skin, eyes and respiratory tissue.
- Reacts vigorously with water or moist air, releasing heat and hydrogen chloride fumes.
- Fire or decomposition can produce corrosive phosphorus and chlorine-containing gases.
- Vapors are heavier than air and may collect in low or confined areas.
- Containers may rupture if heated or contaminated with water.
- Runoff from firefighting or spill control may remain acidic and toxic.
- Contact with metals may increase corrosion and gas-generation hazards.
Chemical Identity & Physical Properties
It is typically a colorless to pale yellow liquid with a sharp, irritating odor. Vapors are heavier than air and the material fumes on exposure to moisture.
| Also known as | Benzenephosphonic dichloridePhenylphosphonic dichloridePhenylphosphonyl dichlorideDichlorophenylphosphine oxide |
| CAS Number | 824-72-6 |
| Appearance | Colorless to pale yellow liquid with a pungent, irritating odor. Fumes in moist air due to reaction with atmospheric moisture. |
| Flash Point | Not readily flammable but may decompose on heating |
| Boiling Point | 258C (496F) with decomposition |
| Vapor Density | 6.6 (heavier than air) |
| Water Reactivity | Reacts vigorously with water producing heat and corrosive fumes of hydrogen chloride and phosphonic acid |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 2798
Extinguishing Media
Dry chemical, CO2, dry sand; avoid water-based agents due to vigorous hydrolysis reaction
PPE Requirements
⚠️ Level B minimum required; SCBA mandatory; full chemical-resistant suit; neoprene or butyl rubber gloves; face shield with goggles
Use Level B or higher chemical protection with SCBA, face and eye protection, and gloves compatible with acid chlorides. Upgrade protection for heavy vapor or unknown concentrations.
Isolation & Evacuation
ERG 137: Initial isolation 50m in all directions; Protective Action Distance 0.1 km (day) / 0.3 km (night) for spills; evacuate immediate area if fire involved
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 137).
First Actions for a UN 2798 Incident
- Call 911 and the emergency response number shown on the shipping papers or container documents.
- Keep unauthorized personnel away and establish an isolation perimeter before entry.
- Stay upwind, uphill and upstream; keep responders out of vapors, dusts and runoff.
- Avoid breathing vapors, dust, mist or smoke and avoid skin or eye contact.
- Do not touch damaged containers or spilled material unless properly trained and protected.
- Ventilate confined spaces only when personnel are trained, equipped and monitored.
- Use ERG guidance, SDS, shipping papers and air monitoring to confirm protective actions.
Advertisement
📋 Copy & Share Field Card
UN 2798 — Benzene phosphorus dichlorideHAZMAT RADIO NOTE — UN 2798
Product: Benzene phosphorus dichloride
Class 8 / Corrosive / ERG 137
PPE: Level B minimum required; SCBA mandatory; full chemical-resistant suit; neoprene or butyl rubber gloves; face shield with goggles
ISOLATION: ERG 137: Initial isolation 50m in all directions; Protective Action Distance 0.1 km (day) / 0.3 km (night) for spills; evacuate immediate area if fire involved
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 2798 — Benzene phosphorus dichloride
Class: 8 | Placard: Corrosive | ERG Guide: 137
Appearance: Colorless to pale yellow liquid with a pungent, irritating odor. Fumes in moist air due to reaction with atmospheric moisture.
Water Reactivity: Reacts vigorously with water producing heat and corrosive fumes of hydrogen chloride and phosphonic acid
Extinguishing: Dry chemical, CO2, dry sand; avoid water-based agents due to vigorous hydrolysis reaction
PPE: Level B minimum required; SCBA mandatory; full chemical-resistant suit; neoprene or butyl rubber gloves; face shield with goggles
Isolation: ERG 137: Initial isolation 50m in all directions; Protective Action Distance 0.1 km (day) / 0.3 km (night) for spills; evacuate immediate area if fire involved
— Key Hazards —
• Liquid and vapors are corrosive and toxic to skin, eyes and respiratory tissue.
• Reacts vigorously with water or moist air, releasing heat and hydrogen chloride fumes.
• Fire or decomposition can produce corrosive phosphorus and chlorine-containing gases.
— First Actions —
• Call 911 and the emergency response number shown on the shipping papers or container documents.
• Keep unauthorized personnel away and establish an isolation perimeter before entry.
• Stay upwind, uphill and upstream; keep responders out of vapors, dusts and runoff.
• Avoid breathing vapors, dust, mist or smoke and avoid skin or eye contact.
SOURCE: allfirefighter.com/hazmat/un/benzene-phosphorus-dichloride-un-2798 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
UN2798 Benzene phosphorus dichloride Cls8 ERG137 | allfirefighter.com/hazmat/un/benzene-phosphorus-dichloride-un-2798SMS / 160 CHAR
Use for: Quick text to command or incoming units. Fits in a single SMS.
⚠️ Quick-reference only. Always use current ERG + SOP/SOG for incident-specific actions.
Page: https://allfirefighter.com/hazmat/un/benzene-phosphorus-dichloride-un-2798
Advertisement
Frequently Asked Questions about UN 2798
Yes. It hydrolyzes vigorously, releasing heat and corrosive hydrogen chloride fumes.
It is not treated as a readily flammable liquid, but heating can produce dangerous corrosive and toxic gases.
Dry chemical, carbon dioxide or dry sand are preferred; avoid water-based agents on the product.
Moisture reaction and fire can release corrosive fumes that can injure the airway even at low visible vapor levels.
Confirm the exact product, container condition and SDS before choosing neutralization or container-handling tactics.
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.