Probably be proved wrong here but if memory serves me right there mustn't be any gap more then 3mm wide at any point.

The doors wouldn't comply with the modern standard but probably complied when they where installed. But equally we don't want to be ripping perfectly good fire doors out just because the standard has moved on. Each situation is going to be different to whether you need to do anything to the doors from total replacement to maybe retro fitting new seals. This could depend on alternative means of escape. fire detection within the building (smoke or just manual call points) use of the building (offices or sleeping accommodation) users familiarity with the building Alternative escape staircases. Hopefully that may be of use but someone will need to make a judgement call if they are suitable but rest assured that there are millions of fire doors that don't have cold seals or intumescent strips. Ensuring the doors are in good condition and fully close are just as important as well as ensuring they aren't wedged open with a fire extinguisher which seems all to common even these days. Phil