Misty Shape Ghost Picture

Jenny Belew sent us this fascinating ghost picture of a misty shape captured in a bomb shelter hallway. If there is no glass in the door (and Jenny said there wasn't), then this looks to be a vaporous apparition:

"My friend and I decided to explore an old bomb shelter at about 10:30 last Friday night (1/5/07). We shot many photos inside the shelter with her new digital camera (using her flash) and they all simply showedexactly what we were taking pictures of....except this one. She had turned around and took a photo of the entrance of the shelter. The night was clear...no humidity...there was no smoke (even though you seemy hand holding a candle...it was a dripless/smokeless emergency candle). We felt nothing strange...no eerie feelings or cold spots...just having fun exploring. In the entry way you can see a misty shape...there was no glass for the flash to reflect on and no light sources outside of the door. The thing that is slanted over theentrance is a heavy metal door that has fallen over time. I have zoomed in on this photo many times and cannot figure out what the mist is coming from. What do you think?"