Question:
Does anyone have an idea what sort of sensors fire alarms are supposed to have in different countries, or in different types of buildings, etc.? Do most fire alarm systems found in (any kind) of building detect smoke or heat? Is the type of sensor which is used dependent on some sort of legal requirement? Is there a global organization determining some sort of fire safety code?

Answer: The place to start is the US National Bureau of Standards, which started research on this sort of thing in 1915. Fire safety codes tend to be local (i.e. municipal or state- wide, not national) even in Europe. The NBS must have its own US government web site by now.