On 30/04/2021 10:13, R D S wrote:
The ceiling and wall/ceiling corner above our boiler is slightly grey
having got that way over some years from previously 'is the ceiling a
bit grey there' to now 'it definitely is, yes'.

There's no CO2, there are 2 detectors in there.

I suppose the sensible answer is get someone in? Or is this normal to
some degree?

Its warm, and so will convect a current of air up against the ceiling.
Dust in the air will do the rest.

--
Cheers,

John.

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