We've got a problem with the automatic smoke vent in one of our staircases, in that it's not opening when the alarm triggers.

So we got someone out to look at it (that was itself a problem - we tried four companies before one would turn up, despite us being happy to pay someone even for this initial look-at-it-and-suck-your-teeth vist).  Anyway, they turned up, looked at it, sucked their teeth, and started complaining that it doesn't meet regs, opening needs to be twice the size, suspended ceiling needs changes, etc etc.

I suspect it may well need to be twice the size, if the building was built now, but normally building regs changes don't apply retrospectively, and there has never been any previous indication of concern that it wasn't compliant when built.  However, I'm struggling to find whether that applies to smoke vents or whether there has been some change that does apply retrospectively - does anyone have any pointers?

Also, can anyone recommend a smoke vent works / servicing company in the South East (the building is in Surrey, inside the M25)? We are fully prepared to throw money at fixing it if necesary, but I don't want to replace roof structure unless essential (making the opening larger will require a new roof structure because it currently fills the gap between structural timber beams) but it seems to be difficult to find anyone that wants our money...

Unless you can repair what is already present the works would be considered refurbishment which then takes you in to the undesired area of complying with current regulations.

Approved Document B of the building regs refers to the "free area" of a smoke vent and that the aerodynamic free area is determined using BS EN 12101-2.

I do not have a copy of the standard - current version 2017 previous 2003.

It may be this standard which has influenced the comment.

BS 9999:2017 also mentions BS EN 12102-2 as containing the calculation but then goes on to quote a minimum aerodynamic free area of 2.0 m2

I don't know what the regs are saying and its all right saying you don't have to retrospectively alter your system but it may be because the calculations have changed and to remove the required smoke from the area you may need twice the extraction units you have now.

From a fire safety point of view it would be more helpful the remove the smoke as fast as you can.