☣️ UN 1341 • CLASS 4
Phosphorus sesquisulphide, free from yellow and white phosphorus
Placard: Flammable Solid. 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 1341
Class: 4
Placard type: Flammable Solid
ERG: Guide 139 (check current ERG)
Isolation: ERG 139: isolate spill/leak area 50m in all directions; for large spill isolate 100m; if fire, isolate 800m and evacuate downwind
Chemical & Response Details
| Also known as | Phosphorus sesquisulfideTetraphosphorus trisulfideP4S3Phosphorus trisulfideSesquisulfide of phosphorus |
| CAS Number | 1314-85-8 |
| Appearance | Yellow to greenish-yellow crystalline solid with a distinctive sulfur-like odor. Moisture-sensitive and may fume in moist air. |
| Flash Point | Not applicable (solid) |
| Boiling Point | Decomposes at approximately 407-408C (765-766F) |
| Vapor Density | Not applicable (solid) |
| Water Reactivity | Reacts with water producing toxic hydrogen sulfide (H2S) and phosphoric acid; may ignite spontaneously in moist air |
| Extinguishing | Dry sand, dry chemical, soda ash; DO NOT use water or foam |
| PPE | ⚠️ Level B minimum with full-face SCBA; chemical-resistant suit required; avoid all moisture contact |
| Isolation | ERG 139: isolate spill/leak area 50m in all directions; for large spill isolate 100m; if fire, isolate 800m and evacuate downwind |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- Produce flammable and toxic gases on contact with water.
- May ignite on contact with water or moist air.
- Some react vigorously or explosively on contact with water.
- May be ignited by heat, sparks or flames.
- May re-ignite after fire is extinguished.
- Some are transported in highly flammable liquids.
- Containers may explode when heated.
- Runoff may create fire or explosion hazard.
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 1341 — Phosphorus sesquisulphide, free from yel HAZMAT RADIO NOTE — UN 1341
Product: Phosphorus sesquisulphide, free from yellow and white phosphorus
Class 4 / Flammable Solid / ERG 139
PPE: Level B minimum with full-face SCBA; chemical-resistant suit required; avoid all moisture contact
ISOLATION: ERG 139: isolate spill/leak area 50m in all directions; for large spill isolate 100m; if fire, isolate 800m and evacuate 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 1341 — Phosphorus sesquisulphide, free from yellow and white phosphorus
Class: 4 | Placard: Flammable Solid | ERG Guide: 139
Appearance: Yellow to greenish-yellow crystalline solid with a distinctive sulfur-like odor. Moisture-sensitive and may fume in moist air.
Water Reactivity: Reacts with water producing toxic hydrogen sulfide (H2S) and phosphoric acid; may ignite spontaneously in moist air
Extinguishing: Dry sand, dry chemical, soda ash; DO NOT use water or foam
PPE: Level B minimum with full-face SCBA; chemical-resistant suit required; avoid all moisture contact
Isolation: ERG 139: isolate spill/leak area 50m in all directions; for large spill isolate 100m; if fire, isolate 800m and evacuate downwind
— Key Hazards —
• Produce flammable and toxic gases on contact with water.
• May ignite on contact with water or moist air.
• Some react vigorously or explosively on contact with water.
— 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/1341 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN1341 Phosphorus sesquisulphide, free from yellow and white phosphorus Cls4 ERG139 | allfirefighter.com/hazmat/un/1341SMS / 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/1341
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FAQ
Produce flammable and toxic gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Containers may explode when heated. Runoff may create fire or explosion hazard.
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 B minimum with full-face SCBA; chemical-resistant suit required; avoid all moisture contact
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 139 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.