A fire is going to break out in one part of the building. A prelimnary Google search has given me some info on combustibility of structures. From what I've turned up, I think that it would make sense that Arkham would be a non-combustible structure--steel and concrete with an asphalt roof and foam insulation. A fire breaks out in an office on the top floor. (If it at all matters, one of the inmates manages to surreptitiously spill a liquid on a floor in one of the offices. By itself it does nothing. However, later that day, when the custodial staff come to clean, the substance reacts with the chemicals in the cleaner. The warm air coming from the heating vents is sufficient to ignite the mixture. There's a rug on the floor, curtains at the windows and wooden furniture. In a world with Joker venom and fear gas, I'm not going into specifics about what chemicals would be needed for such a reaction, or bothering to name the components. Basically, we've got a fire on an upper floor that will spread through the duct system. A couple of people will be trapped.)
1) a) Is it realistic that there would be a fire hydrant on the asylum grounds? The river is right there, but I'd rather avoid the issue of an inmate having to scale a security fence, right at a time when the guards would be expecting someone to try to slip away in the confusion if it's at all possible to move the plot some other way.
b) If so, how can one access the water?
c) I understand about hot air rising and cold air sinking, but I'm guessing that the fire would still spread downward. If so, would the increasing heat have any effect on the water coming out of the fire hydrant? (I'm guessing no, but I'd rather be sure.) I'm guessing that the fire would probably spread the breadth of the upper floor first before spreading to a lower level, is this correct?
2) The fire department won't be able to get there immediately. If I want the building to be by-and-large salvageable, say major fire damage on the top floor where the fire is, but still structurally sound on the floors below (I see Arkham as having 5 storeys. I need it to be inhabitable from the third level downward), can this be accomplished? How quickly would the air system need to be shut down?
3) I have no idea how realistic this is in present day mental institutions, however, going by the 'canon trumps real-life' rule, Arkham does have water cannons for use in bringing 'uncooperative' patients to heel. Do these devices have their own water tank, or would they need to be connected to a hydrant or water pipe? And how high could one be aimed?
4) A man with perfectly healthy lungs but no protective clothing wraps water-soaked blankets around himself and drapes another one over his head. He's breathing through a water-soaked kerchief. Or he can grab a gas mask from a first aid locker or something if he has to. Assuming that the stairs hold and the roof doesn't fall in on him,how long could he probably survive and emerge with nothing more severe than 1st to 2nd degree burns and smoke inhalation? (I.E. no permanent disfigurement or long-term after effects. If there are other injuries he can sustain within those parameters, I'm open.)