Office boiler flues and ventilation system

[Hagbard]

This is not a DIY enquiry, but I'm wondering if any of the gas experts on here could comment.
I work in a 3 storey office block which is one year old. Each floor is heated by 3 fan flued condensing boilers. I don't know their make or rated size, but they're about the same size as domestic ones.
On the same wall as the boiler flues are the intake grilles for the forced air ventilation system. These grilles are about 600mm square and are about 1.5 metres from the boiler flues.

Every now and then the floor I work on is plagued by an unpleasant smell coming from the ventilation system, which varies between sweaty socks and sh1t. The building's 'engineers' have been unable to trace the cause of this intermittent smell. The smell was there again today, and I noticed in passing that the plumes from the boiler flues were being blown by the wind back against the wall and over the intakes for the ventilation system.
Could this unpleasant smell be POCs? What is the minimum distance from a boiler flue to a forced air intake?

 

[ChrisR]

The minima are less than 1.5m.
But you have pocs entering the system if you can see the plume going across a forced intake. Yes, they smell pretty unleasant.
Call H&S.
If I were there I'd quite cheerfully say the gas had to be cut off until the matter is resolved. And I wouldn't take NO for an answer.
Pocs normally contain only C02 and water (+smelly traces), so aren't poisonous as such. You only get carbon monoxide if there's something wrong with the boiler, but you never know.

 

[Hagbard]

Thanks for the reply Chris. The engineers are (allegedly) on their way. In the meantime, the smell has gone - though the wind has changed as well.