Toluene and Xylene: Aromatic Solvent Uses, Hazards and SDS Differences

Toluene and xylene are aromatic hydrocarbon solvents that are frequently traded together and often confused. Both come from petroleum refining, both are flammable, and both are used in coatings, but their classification, composition and some regulatory details differ. If you sell either, your documents have to be specific.

Toluene

Toluene (methylbenzene, CAS 108-88-3) is a clear liquid with a sweet, paint-thinner smell. Its main uses are as a solvent in paints, thinners, adhesives, inks and rubber cement, a feedstock for benzene, xylene and other chemicals, a component of petrol that raises octane, and a reagent in pharmaceutical and chemical manufacture. It is a single, defined substance with a flash point around 4 degrees Celsius.

Xylene

Xylene is not one substance but a group of three isomers: ortho-, meta- and para-xylene, each with its own CAS number, plus ethylbenzene. Commercial mixed xylenes (CAS 1330-20-7) typically contain all three and often 10 to 20 percent ethylbenzene. It is used as a solvent in paints, coatings and printing, as a cleaning agent, in laboratory histology as a tissue clearing agent, and as a feedstock. Para-xylene is further processed into terephthalic acid for polyester (PET). Always say which grade you supply: mixed xylenes, a single isomer, or a solvent blend, as the composition affects both classification and customer acceptance.

Hazard classification

Toluene is classified as a highly flammable liquid (category 2, H225), as a skin irritant (H315), as suspected of damaging the unborn child (reproductive toxicity category 2, H361d), as causing drowsiness or dizziness (H336), as causing damage to organs through prolonged exposure (H373), and, importantly, as an aspiration hazard (H304: may be fatal if swallowed and enters airways). The signal word is Danger, with flame, health hazard and exclamation mark pictograms.

Xylene is classed as flammable (category 3, H226), harmful by inhalation and skin contact (H332, H312), and a skin and eye irritant (H315, H319) with respiratory irritation (H335) and an aspiration hazard (H304) in many entries, signal word Danger or Warning depending on the entry and grade. Because toluene carries a reproductive toxicity classification and mixed xylene typically does not, a blend of the two needs a calculated classification, not a copy of either SDS. Our mixture classification guide explains the method.

Exposure and handling

Both depress the central nervous system, causing headache, dizziness, nausea and, at high levels, unconsciousness, and both can defat the skin leading to dermatitis. Use ventilation or local exhaust, solvent-resistant gloves (nitrile is often poor for aromatic solvents, so use fluoroelastomer or laminate gloves for prolonged contact), splash goggles and, where limits are exceeded, respirators with organic vapour cartridges. Occupational exposure limits for both are set in many jurisdictions, and some are quite low for toluene because of reproductive concerns.

Storage and transport

Treat as flammable liquids. Ground and bond containers, avoid ignition sources, and store away from strong oxidisers, nitric acid and halogens. Vapours are heavier than air and can travel. Transport is Class 3, with toluene typically packing group II and xylene packing group II or III depending on flash point. Check the current UN numbers. For more on how flash point sets flammability categories, read our flash point guide.

The data we hold appears on the toluene page and the xylene page. For a third solvent with a very different hazard profile, see our acetone guide.