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?

  • 2
    Have you called your local fire department in? They should have multiple gas detectors they can bring to the picture... Nov 1, 2019 at 1:32
  • Thanks, I'll ask and provide feedback Nov 1, 2019 at 1:34
  • 1
    Hello, and welcome to Home Improvement. There's no way we could guess at the problem, let alone provide you with a safe answer. And, you should probably take our tour so you'll know how best to participate here. Nov 1, 2019 at 2:06
  • 2
    I'm voting to close this question as off-topic because it's about categorizing poisonous gases. Nov 1, 2019 at 2:06
  • 3
    The fire department suggestion is a good idea, they'd probably be happy for the chance to use their equipment in a real setting. In the meantime, you should be able to find inexpensive chemical-based detectors. For example, you can get CO detection cards, like this one or this one. Home Depot has other gas-detection products that are similar, if the CO doesn't pan out. Nov 1, 2019 at 2:53

1 Answer 1


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.

This sounds very much like Carbon Monoxide(CO) poisoning. It saturates your blood, which slowly suffocates you by preventing your blood from carrying oxygen (it binds better to your hemoglobin). It takes your body some time to recover from it.

You've covered a lot of sources, but does anyone else in the building have something that burns... well, any kind of gas? CO is colorless and odorless, and if someone has, say, an improper venting of their gas heater/stove/grill it could very well be dumping CO exhaust into your area.

one subterranean level below our meeting room

If this is a garage, it could also be a potential CO source. Many older buildings are not sealed, and if this is an underground garage it could easily concentrate the CO and let it seep into your area.

Another potential source is a natural gas leak. The gas company adds Mercaptan to give it its distinctive smell, but Mercaptan is heavier than air, while natural gas can rise. If a natural gas leak were in the basement, it's possible the natural gas makes it up without the Mercaptan.

Buy a Carbon Monoxide detector

They're not terribly expensive and it can tell you if that's your problem. If you buy a combo smoke detector unit, you can just keep it as an extra smoke detector as well.

  • CO is lighter than air so low lying areas are no more likely to have CO than other areas; however, if the low lying area has poor ventilation (many do) and CO is present, then you could have a problem... Nov 1, 2019 at 2:12
  • 2
    @JimmyFix-it Exactly. A dangerous assumption is that because you don't smell the gas doesn't mean it's not there. A stagnant basement full of gas is a real possibility, especially in a 100+ year old building
    – Machavity
    Nov 1, 2019 at 2:14
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    It depends on the location. Pennsylvania, USA, for example, has at least one uninhabitable area due to a slow-burning coal-mine fire releasing carbon monoxide, coming from underground: en.wikipedia.org/wiki/Centralia_mine_fire Nov 1, 2019 at 2:39
  • The detector is on it's way, thanks for the help. If anyone stumbles across this, here's a useful guide on how to understand the output:firepros.com/how-to-read-a-carbon-monoxide-detector Nov 1, 2019 at 9:06
  • Carbon monoxide exposure leaves an exceptionally bad headache. I can't imagine any short term affects of radon ;where did you get that info ? Nov 1, 2019 at 15:03

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