What chemical is MOST commonly used for huffing?

Toluene is the chemical most commonly associated with huffing, which is a form of inhalant abuse. Toluene is a solvent found in various household products, such as paint thinners, adhesives, and nail polish removers. When inhaled, it produces psychoactive effects, leading some individuals to misuse it for a quick high. The appeal of toluene is partly due to its availability and the rapid onset of effects it provides.

The other options, while they may have associated risks, are less commonly used in the context of inhalant abuse. Ammonia can be irritating and is typically found in cleaning products, but it is not sought after for its psychoactive effects. Perfumes might be inhaled for their scent but do not have the same intoxicating effects as toluene. Carbon monoxide, a colorless and odorless gas, is dangerous and can lead to poisoning, but it is not commonly abused for its effects. Therefore, toluene stands out as the primary chemical associated with huffing among the provided choices.