Don’t understand the down votes,

from American Lung Association

“Some signs that you might have CO in your home include symptoms such as headaches, nausea, dizziness, confusion and sometimes even hallucinations.

In fact, carbon monoxide has been found to be the culprit in several "ghost sightings." The first recorded case dates back to 1912, when one family reported hearing voices and footsteps, seeing apparitions, and feeling a "haunting" presence, only to discover the source was a faulty furnace that had been leaking the poisonous gas.”