Haunted house
Pesticides can cause the same types of hallucinations as carbon monoxide. Recreational drugs such as LSD and methamphetamine can cause hallucinations. Unpleasant hallucinations are known in the recreational drug community as a "bad trip". Drug users are usually, but not always, aware that they are experiencing hallucinations related to the drug, at least after they become sober again. Toxic mould, which can produce hallucinogens, has also been linked to haunted houses.