We've recently established an office in North America, and the building has an articulaing fire escape - the upper storeys are fixed ladders and cantilevering platforms projecting out from the wall, and the last storey to the ground there's a ladder that swings down and automatically extends the bottom bit (I think just by the weight on it - you start climbing down it and it extends automatically).

It occurs to me that this sort of thing frequently appears in USA film and TV, but I've never seen it in the UK. I assume there are rules that mean it's not allowed, but out of curiosity, does anyone know what rules? 

The followup is what would you do about this?  It's normal in that region, it looks a bit dicey to me.  When we do a fire drill do we let staff try it out?  I'm mindful that in the UK if we had people using fixed ladders on the outside of a building we'd have rather more controls on it.  I'm also mindful of  https://en.wikipedia.org/wiki/Fire_Escape_Collapse (caution - photo of imminent death).

…and of course in the US there are no national  laws about this sort of thing. Each state will have is own rules and there is also likely to be local municipal codes.