What is Cyclohexane?

Cyclohexane is a cycloalkane with the molecular formula C6H12. It is a colourless flammable liquid with a mild, sweet odour resembling that of chloroform or benzene that occurs naturally in crude oil, volcanic gases, and cigarette smoke but is also produced synthetically to be used as a solvent in numerous industries.

What is Cyclohexane used for?

Solvent: Dissolves cellulose ethers, lacquers, resins, fats, waxes, oils, bitumen, and crude rubber.

Perfume Manufacturing

Surface Coatings: Used in lacquers.

Nylon Production: In adipic acid synthesis for nylon 66 and caprolactam synthesis for nylon 6.

Paint and Varnish Remover

Essential Oils Extraction

Analytical Chemistry: For molecular weight determinations.

Chemical Manufacturing: Produces adipic acid, benzene, cyclohexyl chloride, nitrocyclohexane, cyclohexanol, and cyclohexanone.

Solid Fuel Production: For camp stoves.

Fungicides: Slight fungicidal action in formulations.

Recrystallising Agent: For steroids and glass substitutes.

Organic Synthesis and Adhesives Manufacturing

Sources and Routes of Exposure

Sources of Emission

• Industry Sources: Main sources include petroleum refining, automotive repair shops, and commercial printing and publishing.
• Diffuse Sources: Small facilities below threshold limits.
• Natural Sources: Found in crude petroleum and released by plants and volcanoes.
• Transport Sources: Detected in motor vehicle exhaust.
• Consumer Products: Used as a solvent, oil extractant, paint and varnish remover, and in solid fuels.

Routes of Exposure

• Inhalation: Breathing in contaminated air.
• Ingestion: Consuming contaminated food or water.
• Skin Contact: Absorption through the skin.
• Cyclohexane does not stay in the body long; it breaks down and is expelled in breath and urine.

Health Effects

The impact of cyclohexane on health varies based on concentration and exposure duration. Key points include:

• Short-Term Exposure: Breathing high amounts can harm the nervous system, causing headaches, anaesthesia, tremors, and convulsions.
• Eye Contact: Liquid or vapour can damage eyes.
• Long-Term Exposure: Effects from low levels over time are unclear, and no sufficient data exists on cancer or reproductive effects. Animal studies show repeated high exposure causes nervous system issues, eye damage, and respiratory effects. Ongoing research is examining reproductive effects on animals.

Cyclohexane Safety

First Aid Measures

• Eye Contact: Remove contact lenses and flush eyes with water for 15 minutes. Seek medical help.
• Skin Contact: Rinse skin with water, cover irritated areas, remove contaminated clothing, and wash clothing before reuse. Get medical attention.
• Serious Skin Contact: Use disinfectant soap and anti-bacterial cream; seek medical help.
• Inhalation: Move to fresh air. If not breathing, perform artificial respiration. Get medical attention.
• Serious Inhalation: Evacuate and loosen tight clothing. Administer oxygen if needed and seek medical attention.
• Ingestion: Do not induce vomiting unless directed. Get medical attention if symptoms appear.

Fire & Explosion Information

• Cyclohexane is highly flammable and slightly explosive in the presence of open flames and sparks.
• It is insoluble in water. Use dry chemical powder for small fires and water spray or fog for larger fires.
• Vapours can travel to ignition sources and cause flashbacks.
• Mixing hot cyclohexane with liquid dinitrogen tetraoxide can cause explosions.

Exposure Controls & Personal Protection

Engineering Controls

• Use exhaust ventilation to keep vapour concentrations below safety limits. Have eyewash stations and safety showers nearby.

Personal Protective Equipment

Recommended PPE for handling cyclohexane includes:

• Splash goggles
• Lab coat
• Approved vapour respirator
• Gloves

For Large Spills:

• A full protective suit, splash goggles, vapour respirator, boots, gloves, and a self-contained breathing apparatus are recommended. Consult a specialist before handling.

Regulation

Occupational Exposure Limits

United States

• OSHA: The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for cyclohexane is 300 ppm (1050 milligrams per cubic meter (mg/m3) as an 8-hour time-weighted average (TWA) concentration [29 CFR 1910.1000, Table Z-1].
• NIOSH: The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for cyclohexane of 300 ppm (1050 mg/m3) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].
• ACGIH: The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned cyclohexane a threshold limit value (TLV) of 300 ppm (1030 mg/m3) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 17].

Australia

• Safe Work Australia: Safe Work Australia has established an 8-hour time-weighted average (TWA) for cyclohexane of 350 mg/m3 and a short-term exposure limit (STEL) of 1050 mg/m3.