Inhalants

Intoxicative inhalants are a broad range of intoxicative drugs whose volatile vapors are taken in via the nose and trachea. They are taken by room temperature volatilization or from a pressurized container (e.g., nitrous oxide), and do not include drugs that are sniffed after burning or heating. For example, amyl nitrite and toluene are considered inhalants, but tobacco, marijuana, and crack are not, even though the latter are also inhaled as smoke.

While some inhalant drugs are used for medical purposes, as in the case of nitrous oxide (a dental anxiolytic), this article focuses on inhalant abuse as recreational drugs that are used for their intoxicating effect. Inhaling volatile substances because of their intoxicating effect is called huffing.

Source: Wikipedia.