UN 1581 — Chloropicrin and methyl bromide mixture
Placard: Toxic Gas. ERG Guide 123. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 1581 is Chloropicrin and methyl bromide mixture, a toxic liquefied gas mixture assigned to ERG Guide 123. It is a fumigant-type hazard with heavy vapors, skin absorption risk and severe respiratory irritation.
Hazard overview: UN 1581 presents toxic gas, heavier-than-air vapor and frostbite/contact hazards. Leaks can collect in low areas, and heated cylinders may vent toxic gas or rupture.
Response guidance: For a UN 1581 incident, responders should verify the product with shipping papers, package markings, SDS and ERG Guide 123. Establish incident command, isolate the area, stay upwind, prevent dust or vapor exposure, control runoff and choose entry or cleanup actions based on monitoring, SDS and local SOP.
Firefighter training notes: Training for UN 1581 should emphasize toxic gas movement, heavier-than-air vapor behavior, cylinder heating, frostbite/contact hazards, SCBA use and downwind protective actions. Use ERG 123, SDS and incident command.
Regulatory context: Chloropicrin and methyl bromide mixture is regulated as a toxic hazardous material. Transportation, workplace exposure, spill reporting, waste handling, storage and environmental requirements may vary by formulation, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, facility documents and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Chloropicrin and methyl bromide mixture should be stored in approved pressure containers in a secure, cool, well-ventilated toxic-gas area away from heat, ignition sources where relevant, incompatible chemicals and unauthorized access. Cylinder protection, leak detection and emergency ventilation should follow SDS and facility procedures.
UN 1581 Quick Details
Common Hazards of UN 1581
- TOXIC liquefied gas mixture; inhalation or skin absorption may be fatal.
- Vapors are irritating and may be corrosive to eyes, skin and respiratory tissue.
- Vapors are heavier than air and may spread along the ground into low or confined areas.
- Contact with liquefied gas may cause frostbite as well as chemical injury.
- Fire may produce irritating, corrosive and/or toxic gases.
- Cylinders or containers may rupture or vent when heated.
- Runoff or water spray may carry toxic contamination.
Chemical Identity & Physical Properties
Colorless to pale yellow liquefied gas mixture with a pungent, tear-producing odor. Heavier than air vapor that can accumulate in low-lying areas.
| Also known as | Chloropicrin-methyl bromide mixturePicfumeTerr-o-gasBromomethane-trichloronitromethane mixtureMethyl bromide-chloropicrin fumigant |
| Appearance | Colorless to pale yellow liquefied gas mixture with a pungent, tear-producing odor. Heavier than air vapor that can accumulate in low-lying areas. |
| Flash Point | Not applicable (non-flammable gas mixture) |
| Boiling Point | Component-dependent: methyl bromide 3.6C (38.5F), chloropicrin 112C (234F) |
| Vapor Density | 3.3-5.7 (heavier than air, depending on mixture ratio) |
| Water Reactivity | Slow hydrolysis in water; chloropicrin component reacts slowly producing corrosive products |
Fireground Response Guidance — UN 1581
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA and chemical protective clothing selected by hazmat specialists for any vapor, liquid or unknown exposure. Level A is often appropriate for close entry because toxic vapor and skin absorption hazards may be severe.
Isolation & Evacuation
First Actions for a UN 1581 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Many vapors are heavier than air; avoid low areas, basements, trenches and confined spaces.
- Avoid breathing vapors, fumes, dust or mist and avoid all skin or eye contact.
- Eliminate ignition sources if a flammable component is present and it is safe to do so.
- Do not touch or walk through spilled material unless properly trained and wearing appropriate protective equipment.
- Isolate the leak area and expand protective actions downwind based on monitoring, wind and ERG Table 1 when applicable.
- Isolate the spill or leak area and expand the perimeter if vapor, dust, fire involvement or unknown concentration is present.
- Use ERG Guide 123, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 1581 — Chloropicrin and methyl bromide mixtureUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.