UN 1145 — Cyclohexane

Cyclohexane, also known as hexamethylene, is a highly flammable liquid with a sweet, gasoline-like odor. It is widely used as a solvent in various industrial applications, including paint, coatings, and adhesives. As a result, first responders may encounter cyclohexane during transportation accidents, industrial fires, or spills. With a large scale of production and transportation, the risk of cyclohexane exposure is significant. The DOT classifies cyclohexane as a Class 3 flammable liquid, and it is essential for first responders to understand its hazards and response procedures. Cyclohexane is a common chemical used in many industries, and its flammability and explosiveness make it a significant concern for emergency responders.

Hazard overview: Cyclohexane is highly flammable, with a flash point of -20°C (-4°F) and a boiling point of 81°C (178°F). Its vapors are heavier than air, with a vapor density of 2.9, and may form explosive mixtures with air. The vapors can travel to the source of ignition and flash back, posing a significant risk of fire and explosion. Prolonged exposure to cyclohexane vapors can cause respiratory irritation, dizziness, and nausea. The LC50 value for cyclohexane is not well-established, but it is known to be toxic at high concentrations. In the worst-case scenario, a large spill or fire involving cyclohexane can lead to a vapor explosion hazard indoors, outdoors, or in sewers, putting first responders and the public at risk. Cyclohexane is insoluble in water, which can affect its behavior in aquatic environments.

Response guidance: In the event of a cyclohexane spill or fire, first responders should isolate the area 50m in all directions and evacuate 300m downwind for large spills. The correct suppression agent for cyclohexane is AFFF foam, alcohol-resistant foam, dry chemical, or CO2. Decontamination procedures should be followed, and CHEMTREC should be contacted for guidance. It is essential to use Level B minimum PPE, including SCBA and chemical-resistant suits, when responding to cyclohexane incidents. First responders should also be aware of the potential for vapor explosion hazards and take necessary precautions to mitigate this risk.

Firefighter training notes: First responders should be trained to recognize the hazards of cyclohexane and respond accordingly. A common tactical error when responding to cyclohexane incidents is underestimating the risk of vapor explosion. First responders should be aware of the potential for vapor explosion hazards and take necessary precautions to mitigate this risk. The ICS position of Operations Section Chief should be notified of any cyclohexane incidents, and mutual aid criteria should be established to ensure adequate resources are available to respond to the incident.

Regulatory context: Cyclohexane is classified as a Class 3 flammable liquid by the DOT. The OSHA PEL for cyclohexane is 300 ppm, and the TLV is 100 ppm. Cyclohexane is not listed on the CERCLA list, but it is subject to regulations under the Clean Air Act and the Resource Conservation and Recovery Act.

Storage & handling: Cyclohexane should be stored in a well-ventilated area, away from heat sources and ignition sources. The temperature limit for storing cyclohexane is not well-established, but it should be kept away from incompatible materials such as strong oxidizers and acids. The container type for storing cyclohexane should be a tightly sealed, chemical-resistant container, and the ventilation standard should be designed to prevent the accumulation of vapors.