I thought that the original reason for moving from springs to foam seating was the fire risk on seats with springs was a lot higher than the fire-retarded foam. These appear to be made with small pocket springs in these - what changed?
Metal springs obviously don't burn, from what I have read it seems to have been to do with funnel effect, basically a fire would grow in a draft along the void. Filling with solid foam meant no void so was assumed safer.
Although what I looked at related to aircraft seats, what was subsequently realised was the foam has gaps, it doesn't totally fill the space (slots are left for usb and entertainment cables etc). And of some trains there are power sockets. So presumably whilst old risk of dropped cigarette has gone, there is a new risk of electrical fire.
Historically the idea of foam seem to be a bit of a disjointed policy that dates back to cigarettes being smoked, as the foam was often installed in vehicles fitted with cables that gave off toxic fumes from their insulation if there was a fire.
It seems there is a realisation that fire rarely kills from burning, but toxic fumes incapacitate people and bodies get discovered unburnt, but dead from suffocation whilst unconscious. There was a reference to a minor train fire in 1950s which although fire was put out some ladies had died in a compartment apparently smiling. It was eventually discovered smouldering varnished panels had given off toxic cellulose fumes that had killed them.
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