☣️ UN 3255 • CLASS 4
tert-Butyl hypochlorite
Placard: Spontaneously Combustible. 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 3255
Class: 4
Placard type: Spontaneously Combustible
ERG: Guide 135 (check current ERG)
Isolation: ERG 135: Isolate spill 25-50m all directions. If tank/rail car involved in fire, isolate 800m all directions and evacuate 800m.
Chemical & Response Details
| 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. |
| 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. |
Chemical details are general reference only. Always verify with current SDS, ERG, and SOP/SOG.
Common hazards (high level)
- 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.
First actions (field-minded)
- 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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UN 3255 — tert-Butyl hypochlorite HAZMAT 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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FAQ
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.
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.