I’m glad you asked. Yes, they are! (From Wikipedia)
Who knew!
Many of the phenomena generally associated with haunted houses, including strange visions and sounds and feelings of dread, can be attributed to carbon monoxide poisoning, as its symptoms include confusion, delirium, emotional disturbances, and hallucinations.[22][130] In one famous case, carbon monoxide poisoning was clearly identified as the cause of an alleged haunting. Dr. William Wilmer, an ophthalmologist, described the experiences of one of his patients in a 1921 article published in the American Journal of Ophthalmology. “Mr. and Mrs. H.” moved into a new home, but soon began to complain of headaches and fatigue. They began to think they were hearing bells and footsteps during the night, accompanied by strange physical sensations and sightings of mysterious figures. When they began to investigate the symptoms, they discovered the previous residents of the house had similar experiences. An examination of their furnace found it to be severely damaged, resulting in incomplete combustion and forcing most of the fumes, including carbon monoxide, into the house rather than up the chimney.[4]
A report published in 2005 described a 23-year old female victim of carbon monoxide poisoning, found delirious and hyperventilating, who thought she saw a ghost while in the shower. A new gas water heater had just been improperly installed in her home, which flooded the house with carbon monoxide when the victim closed all the exterior windows and doors and took a shower
