I'm playing the platinum edition for few years and I dunno for what is the first aid building used. No single peep went there even when he was hurt in an accident. So, for me, the first aids are unused. Do they have any usage in practice? Thenks in advantage. fjx
P.S. Sorry for eventual mistakes. I'm not native English speaker.

The first aid building has an entrance, but you hardly see it. Watch closely to the handles and place the building right!

People will walk into it when they're sick

Hope you didn't know this already ;P