Or maybe it's just an old boiler ?
Anyone read "The english patient" ?
Lot of defusing bombs in there explained well, and several tricks installed to kill defusers as well. Some had timeshift fuses, so after the bombers were away for hours, and the first people began to look and search the rubble for survivors, it would kill them the with a delay. Or two kinds of fuses, one obvious to remove, the other then beginning to start when the fake one was removed. Some real ingenuity when it comes to killing people, especially civilians.
This "Luftmine" or block buster is especially vicious, since it destroyed the lungs of people not being in shelters, for more than a kilometer (radius).
No wonder so much people have to be evacuated in a densely populated area.
Imagine hundreds of those dropped over one city ..