My office has a meeting room that is located on the ground floor with inward facing windows towards the bottom of very small and stuffy open air interior. This area is surrounded by six floors of residential property above and one subterranean level below our meeting room. The building dates from the 1900's. The courtyard in terms of appearance has lots of weird pipes and wires installed ad-hoc over the years alongside open lift shafts.
Every time me and my colleagues enter this room if the meeting is over ~30 mins we leave with symptoms of fatigue, dizziness and a reduced mental ability, it takes about 1-3 hours to overcome these symptoms.
There is no question of complicity on behalf of the business and I'm cleared to buy whatever device is necessary to determine the cause of the issue but I have no idea how to deliver a diagnosis without wasting money. Ideas I've considered are:
Carbon Monoxide? - We have no gas burning appliances and none are in sight in the interior space which is empty.
Is it mains gas? - I can't smell gas.
Is it radon? - There is no history of mining in area.
I've looked online for gas detectors but it seems you can only buy detectors for each type of gas, Butane, Radon and CO are the main ones. Most of these are in the $20 area but can cost up to $200.
Is there a multi gas detector that can detect and indicate the precise cause? Online research does not point conclusively to any of them.
If not, how to proceed?