Volatile substances are chemical elements and compounds that can be readily vaporized). They are characterized by their ability to evaporate quickly at room temperature and pressure. Volatile substances can be classified into two main categories: those that are naturally occurring and those that are synthetic. Naturally occurring volatile substances include nitrogen, carbon dioxide, ammonia, hydrogen, methane, sulfur dioxide, and water). Synthetic volatile substances are often found in household and workplace chemicals, such as spray deodorants, glue, lighter refills, and spray air fresheners.

Volatile substances can have a range of effects on the human body, depending on the substance and the method of exposure. Inhaling volatile substances can result in a decreased rate of breathing, dizziness, hallucinations, and even death. Volatile substance abuse (VSA) is a serious problem that can lead to long-term health problems and addiction.

Examples of volatile substances include:

• Nitrous oxide, also known as "laughing gas"
• Butane gas found in cigarette lighter refills and aerosols
• Alkyl nitrites, better known as "poppers"
• Petrol
• Some industrial glues
• Acetone, found in nail polish remover

In chemistry, a volatile substance is defined as having a high vapor pressure at a given temperature compared with a nonvolatile compound.