A paint thinner is a solvent

Solvent

A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 used to thin oil-based paint

Oil paint

Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil, commonly linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, and varnish may be added to increase the glossiness of the...

s or clean up after their use, although all such solvents have other uses. Commercially, "paint thinner" is usually a name for mineral spirits.

Products used as paint thinners include:

• Mineral spirits
• Acetone
  Acetone
  Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
  
  
• Mineral turpentine
  Mineral turpentine
  Mineral turpentine, also known as turpentine substitute, turps substitute, or just turps is an inexpensive petroleum-based replacement for the vegetable-based turpentine...
  
   (turps)
• True turpentine
  Turpentine
  Turpentine is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-pinene and beta-pinene...
  
  
• Naphtha
  Naphtha
  Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons, i.e., a component of natural gas condensate or a distillation product from petroleum, coal tar or peat boiling in a certain range and containing certain hydrocarbons. It is a broad term covering among the...
  
  
• White spirit
  White spirit
  White spirit [CAS 64475-85-0], also known as Stoddard solvent [CAS 8052-41-3] or mineral spirits, is a paraffin-derived clear, transparent liquid which is a common organic solvent used in painting and decorating. In 1924, an Atlanta dry cleaner named W. J. Stoddard worked with Lloyd E...
  
  
• Methyl ethyl ketone (MEK)
• Dimethylformamide
  Dimethylformamide
  Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...
  
   (DMF)
• 2-Butoxyethanol
  2-Butoxyethanol
  2-Butoxyethanol is an organic solvent with the formula BuOC2H4OH . It is a colorless liquid with a sweet, ether-like odour. It is a butyl ether of ethylene glycol...
  
  , or any of the other glycol ethers
  Glycol Ethers
  Glycol ethers are a group of solvents based on alkyl ethers of ethylene glycol commonly used in paints. These solvents typically have higher boiling point, together with the favorable solvent properties of lower molecular weight of ethers and alcohols. The word "Cellosolve" was registered in 1924...
  
  

Solvents generally used in the production of paint thinners include:

• Ethylbenzene
  Ethylbenzene
  Ethylbenzene is an organic compound with the formula C6H5CH2CH3. This aromatic hydrocarbon is important in the petrochemical industry as an intermediate in the production of styrene, which in turn is used for making polystyrene, a common plastic material....
  
  
• Xylene
  Xylene
  Xylene encompasses three isomers of dimethylbenzene. The isomers are distinguished by the designations ortho- , meta- , and para- , which specify to which carbon atoms the two methyl groups are attached...
  
  
• n-butyl acetate
• Butan-1-ol

While painting or making the paint of proper consistency by addition of thinner liquid there is an exposure to the vapours. ACGIH

American Conference of Governmental Industrial Hygienists

The American Conference of Governmental Industrial Hygienists is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio...

 has established threshold limit value

Threshold Limit Value

The threshold limit value of a chemical substance is a level to which it is believed a worker can be exposed day after day for a working lifetime without adverse health effects. Strictly speaking, TLV is a reserved term of the American Conference of Governmental Industrial Hygienists...

s (TLVs) for most of these compounds. TLV is defined as the maximum concentration in air which, if breathed by a normal person (i.e., excluding children, pregnant women, etc.) in the course of 40 hours work (in US work conditions) per week, day after day through their work life without long-term ill effects. Normally in undeveloped world workers work with much higher exposure to these chemicals with consequent damage to their health.

Recreational Use

Some paint thinners, such as mineral turpentine

Mineral turpentine

Mineral turpentine, also known as turpentine substitute, turps substitute, or just turps is an inexpensive petroleum-based replacement for the vegetable-based turpentine...

, may be abused as inhalant

Inhalant

Inhalants are a broad range of drugs whose volatile vapors are taken in via the nose and trachea. They are taken by volatilization, and do not include drugs that are inhaled after burning or heating...

s. This is an extremely dangerous and potentially addictive form of drug abuse

Drug abuse

Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts...

. Due to the dangers linked with inhaling these solvents, most paint thinners are recommended for use in well ventilated areas to minimize danger.