Anti-revisionist and science historian Dr. Michael Shermer doesn't believe in ghosts, nor does he believe that anyone was ever gassed in the Dachau gas chamber, which suggests that he'd probably be a little sceptical of the following evidence presented by paranormal expert Dennis William Hauck:
DACHAU CONCENTRATION CAMP This former concentration camp is located twelve miles (sixteen kilometers) north of Munich outside the town of Dachau. Built in 1933, it was the first Nazi concentration camp and also the site of gruesome medical experiments performed on unwilling prisoners. The experiments measured the effects on the human body of starvation, drinking seawater, malaria, freezing, electricity, and sudden changes in atmospheric pressure. Seven of Dachau's "doctors" were sentenced to death at the Nuremberg trials. In all, more than two hundred thousand prisoners entered Dachau and between thirty thousand and fifty thousand of them died there. By 1940, disposal of dead bodies became a major problem and a crematorium was built on the grounds. By 1942, mass exterminations were taking place on a daily basis and a larger "more efficient" oven had to be added.
In 1943, still another crematorium was built that incorporated a homicidal gas chamber disguised as a large meeting room. It was located in a housing area referred to as "Barracks X" in the Nazi records. Prisoners would be led into the room for a meeting, then the room was sealed and poisonous gas introduced. There were four other gas chambers at Dachau, some of which were connected directly to shower stalls. German historians insist these were used for disinfectant purposes, but the paranormal evidence seems to contradict these claims. Several reports of disembodied screaming, voices shouting "gas," and naked running apparitions originate from these shower stalls. During a recent visit to Dachau, American tourist Dave Goodwin took a photograph in the shower area that appears to show a ghostly figure running out of the showers.
Dennis William Hauck, The International Directory of Haunted Places, Ghostly Abodes, Sacred Sites, and Other Supernatural Locations, NY: Penguin, 2000, p. 114.
Above is a photograph I've taken (slightly cropped) of Goodwin's photograph as reproduced in Hauck's book.
This is the photographer of the Dachau gas chamber ghost, Dave Goodwin, pictured outside Abu Ghraib prison in Iraq. Goodwin presented evidence in an article written in 2005 that Abu Ghraib is haunted too. He mentions the horrific torture of inmates whilst the prison was run by the Iraqis—no mention of the torture and rape which occurred at Abu Ghraib when it was run by the Americans, i.e. when he was there.