☣️ UN 3255 • CLASS 4
UN 3255 — tert-Butyl hypochlorite
Placard: Spontaneously Combustible. ERG Guide 135. 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 3255 Quick Details
UN 3255
Product name: tert-Butyl hypochlorite
DOT Class: 4
Placard type: Spontaneously Combustible
ERG Guide: 135 (check current ERG)
Initial isolation: ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
Common Hazards of UN 3255
- Flammable/combustible material.
- May ignite on contact with moist air or moisture.
- May burn rapidly with flare-burning effect.
- Some react vigorously or explosively on contact with water.
- Some may decompose explosively when heated or involved in a fire.
- May re-ignite after fire is extinguished.
- Runoff may create fire or explosion hazard.
- Containers may explode when heated.
Chemical Identity & Physical Properties
| Also known as | tert-Butyl hypochloriteHypochlorous acid tert-butyl ester2-Chloro-2-methylpropanet-Butyl hypochloriteTrimethylmethyl hypochlorite |
| CAS Number | 507-40-4 |
| Appearance | Colorless to pale yellow liquid with a pungent, irritating odor. Highly unstable and reactive at room temperature. |
| Flash Point | -9C (16F) |
| Boiling Point | 78-79C (172-174F) (decomposes) |
| Vapor Density | 3.8 (heavier than air) |
| Water Reactivity | Reacts with moisture and water, releasing hypochlorous acid and corrosive fumes. May ignite spontaneously in moist air. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Fireground Response Guidance — UN 3255
Extinguishing Media
Dry chemical, CO2, sand. Do not use water or foam due to water reactivity.
PPE Requirements
⚠️ Level B minimum; SCBA required. Full chemical-resistant suit recommended due to flammability and corrosive vapor hazard.
Isolation & Evacuation
ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
Always confirm protective actions with the current edition of the Emergency Response Guidebook (ERG Guide 135).
First Actions for a UN 3255 Incident
- CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
- Stay upwind, uphill and/or upstream.
- Keep unauthorized personnel away.
- 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 3255 — tert-Butyl hypochloriteHAZMAT RADIO NOTE — UN 3255
Product: tert-Butyl hypochlorite
Class 4 / Spontaneously Combustible / ERG 135
PPE: Level B minimum; SCBA required. Full chemical-resistant suit recommended due to flammability and corrosive vapor hazard.
ISOLATION: ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
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 3255 — tert-Butyl hypochlorite
Class: 4 | Placard: Spontaneously Combustible | ERG Guide: 135
Appearance: Colorless to pale yellow liquid with a pungent, irritating odor. Highly unstable and reactive at room temperature.
Water Reactivity: Reacts with moisture and water, releasing hypochlorous acid and corrosive fumes. May ignite spontaneously in moist air.
Extinguishing: Dry chemical, CO2, sand. Do not use water or foam due to water reactivity.
PPE: Level B minimum; SCBA required. Full chemical-resistant suit recommended due to flammability and corrosive vapor hazard.
Isolation: ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
— Key Hazards —
• Flammable/combustible material.
• May ignite on contact with moist air or moisture.
• May burn rapidly with flare-burning effect.
— First Actions —
• CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper
• Stay upwind, uphill and/or upstream.
• Keep unauthorized personnel away.
• Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters
SOURCE: allfirefighter.com/hazmat/un/3255 | Always use current ERG + SOP/SOGIC BRIEFING
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief. Full chemical + response details.
UN3255 tert-Butyl hypochlorite Cls4 ERG135 | allfirefighter.com/hazmat/un/3255SMS / 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/3255
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Frequently Asked Questions about UN 3255
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper Stay upwind, uphill and/or upstream. Keep unauthorized personnel away.
Level B minimum; SCBA required. Full chemical-resistant suit recommended due to flammability and corrosive vapor hazard.
Water reactivity: Reacts with moisture and water, releasing hypochlorous acid and corrosive fumes. May ignite spontaneously in moist air.. Recommended extinguishing: Dry chemical, CO2, sand. Do not use water or foam due to water reactivity..
ERG Guide 135 recommendation: ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
No. This is a training/quick-reference aid only. Always consult the current ERG Guide 135 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.