Fire Safety Statements

If a building complies with the fire safety standards (e.g. regarding signage) of the building code in effect at the time of the issue of the occupancy certificate (e.g. 1990), do the later, different, requirements of the EPA Regulations 2000 override this? I thought they only apply to developments, i.e. not existing buildings.

I am a bit suspicious of all the changes our Fire Safety firm says are required…..

Thanks for any thoughts on this.