Fire extinguishers in a block of flats are pointless.
By the time a fire is large enough to be noticed and someone has found the extinguisher, it's already too late - even assuming someone knows where the extinguisher is and is able and willing to use it properly.
If a fire is detected (which should be with smoke alarms or a fire alarm system) the only valid actions are:
1 - call the fire brigade,
2 - either people stay in each flat with the doors closed, or evacuate the whole building immediately.
Which 2 is selected depends on factors such as the building construction, layout, size, number of occupants and so on.
In a limited number of circumstances an extinguisher could be used to aid escape from the building if the only exit route was partially blocked by fire, but the idea of putting out a fire with one is totally unrealistic.
Fair point. I guess one in my kitchen could be handy though