This could be a can of worms! People a re sensitive to all sorts of different things and finding out what they could be reacting to, could be like looking for a needle in haystack. Things like new furniture do give off some volatile smelly components but these should not be an issue and they will soon disperse. if you have had carpet tiles glued down find out what sort of glue the contractor used ( Of course they supplied an RA and MS) and how long any solvent will take to disperse. Dust from drill holes for sockets etc. might be an issue so the place needs a good vacuum clean. You can monitor the humidity- check the CIBSE guidelines for this. Finally if after a week or two people are still complaining about the office; causing them headaches etc, try to find out how they are coping with new environment. I have had several occasions where the real issue hasn't been the physical environment just the fact that staff don't like their new office and don't like the people they are sharing it with.