Frankie, ordinary house air con isn’t a problem ( except on sinuses).
It is hospitals, Government buildings or any building of size with a water tower.
Similar with fountains, Judi.
Only the street ones are a problem because they use “dirty”water which the weather warms and cools.
Also it isn’t the stagnant water that actually causes legionnaires, indeed it can be safely swallowed....not that we would want to...but the droplets in the air that are invisibly inhaled into the mouth and nose when fountain/ air on in operation.
All this info came via local Murcian authority who investigated cause of my husband catching it.
They checked everything, shower heads, aircon, taps. All clear, until they checked irrigation system..and wow, trillions of bugs.
So, anyone on mains water, even if not potable, no worries.
Actually of the most dangerous thing, that we ALL utilise, is the car screen washer.
Warmed up stagnant water suddenly spraying over the windscreen.
So ALWAYS ensure windows are closed before using.
Likewise bags of compost .Take care when opening the bag to avoid the spores blowing around.
COVID....that’s another problem that will be solved...just not sure how soon