Benzene

Classification

Flammable liquid, Category 2; Aspiration hazard, Category 1; Skin irritation, Category 2; Serious eye irritation, Category 2; Germ cell mutagenicity, Category 1B; Carcinogenicity, Category 1A; Specific target organ toxicity, repeated exposure, Category 1

Hazard statements

• H225 Highly flammable liquid and vapor.
• H304 May be fatal if swallowed and enters airways.
• H315 Causes skin irritation.
• H319 Causes serious eye irritation.
• H340 May cause genetic defects.
• H350 May cause cancer.
• H372 Causes damage to organs through prolonged or repeated exposure.

Key precautionary statements

• P203 Obtain, read and follow all safety instructions before use.
• P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
• P240 Ground and bond container and receiving equipment.
• P280 Wear protective gloves, protective clothing, eye protection and face protection.
• P301+P316 IF SWALLOWED: Get emergency medical help immediately.
• P331 Do NOT induce vomiting.
• P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing. Rinse skin with water or shower.
• P403+P235 Store in a well-ventilated place. Keep cool.

Most workplaces fall under the OSHA benzene standard, 29 CFR 1910.1028, which sets a PEL of 1 ppm TWA and 5 ppm STEL plus an action level of 0.5 ppm that triggers exposure monitoring and medical surveillance. Operations exempt from that standard fall under Table Z-2 (10 ppm TWA, 25 ppm ceiling, 50 ppm peak for up to 10 minutes). NIOSH treats benzene as a potential occupational carcinogen and recommends 0.1 ppm TWA and 1 ppm STEL. ACGIH lowered its TLV-TWA to 0.02 ppm in its 2024 TLVs. Benzene is absorbed through the skin. State OSHA plans may set different limits.

• Appearance: Colorless to light-yellow liquid; becomes a solid below 42°F (6°C)
• Odor: Aromatic
• Molecular weight: 78.1
• Boiling point: 176°F (80°C)
• Freezing point: 42°F (6°C)
• Flash point: 12°F (-11°C)
• Autoignition temperature: 928°F (498°C)
• Explosive limits: LEL 1.2%, UEL 7.8%
• Vapor pressure: 75 mmHg
• Specific gravity: 0.88
• Water solubility: 0.07%

Inhalation

Irritates the nose and respiratory system. Causes dizziness, headache, nausea, staggering and weakness.

Skin

Irritates the skin and causes dermatitis. Benzene is absorbed through the skin and adds to total body exposure.

Eyes

Causes serious eye irritation.

Ingestion

Can be fatal if swallowed and the liquid enters the lungs. Get medical help immediately and do not induce vomiting.

Target organs

Eyes, skin, respiratory system, blood, central nervous system, bone marrow

Long-term effects

Benzene is a known human carcinogen that causes leukemia. Repeated exposure damages the bone marrow and can lower blood cell counts. It may also cause genetic defects.

Gloves

Silver Shield (laminate), polyvinyl alcohol (PVA) or Viton gloves. Common nitrile, neoprene and latex lab gloves are easily permeated by benzene and are not recommended.

Eyes and face

Chemical splash goggles. Provide an eyewash where benzene is handled.

Respiratory

Work in a fume hood or with local exhaust. NIOSH recommends a pressure-demand self-contained breathing apparatus or supplied-air respirator with full facepiece at any concentration above the REL. Under the OSHA standard, respirator selection follows 29 CFR 1910.1028 and 1910.134.

Clothing

Wear protective clothing that prevents skin contact. Remove clothing promptly if it becomes wet, because it is a fire hazard. Provide a quick-drench shower.

Store in a tightly closed container in an approved flammable liquid cabinet, in a cool, well-ventilated area away from heat, sparks, flame and oxidizers. Post regulated areas where exposure can exceed the PEL, as required by 29 CFR 1910.1028.

Handle in a fume hood or with local exhaust ventilation. Ground and bond containers during transfer, use non-sparking tools and wash thoroughly after handling. Empty containers keep flammable residue.

Keep away from

• Strong oxidizers
• Many fluorides and perchlorates
• Nitric acid

• Remove all ignition sources and ventilate the area.
• Approach from upwind wearing the protective equipment described above.
• Absorb the liquid with an inert material such as vermiculite, sand or earth, and place it in a closed container for disposal.
• Keep the liquid out of sewers, drains and waterways.
• Water spray can be used to cool and disperse vapors.
• Follow ERG Guide 130.

Suitable extinguishing media

• Dry chemical
• Carbon dioxide
• Appropriate foam
• Water spray, to cool containers and disperse vapors

Special hazards

Vapors are heavier than air, collect in low areas and can flash back from a distant ignition source. The liquid floats on water and can spread a fire. Static discharge can ignite vapors. Burning produces carbon monoxide and carbon dioxide. Fight fires from upwind and keep containers cool with water spray.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical. Labels and safety data sheets are required.
• OSHA Benzene Standard (29 CFR 1910.1028): PEL 1 ppm TWA and 5 ppm STEL, action level 0.5 ppm, with exposure monitoring, regulated areas, respirators and medical surveillance.
• OSHA Air Contaminants (29 CFR 1910.1000, Table Z-2): Applies only to operations exempt from 1910.1028.
• CERCLA (40 CFR 302.4): Hazardous substance, reportable quantity 10 lb; RCRA waste number U019.
• EPCRA Section 313 (TRI) (40 CFR 372.65): Listed.
• DOT (49 CFR 172.101): UN1114, Benzene, Class 3, Packing Group II.

• NIOSH Pocket Guide: Benzene
• OSHA Benzene Standard, 29 CFR 1910.1028
• PubChem: Benzene GHS classification
• eCFR: CERCLA hazardous substances, 40 CFR 302.4
• UCSB EH&S Fact Sheet: Benzene