On Wed, 21 Oct 2020 09:38:57 -0700 (PDT),
wrote:

On Wednesday, 21 October 2020 15:02:07 UTC+1, Scott wrote:
That's okay in a single house. The problem is where the
concealed flue runs through a different flat, and
the other owner/occupier is not amenable to having it opened up.
What does 'concealed' mean in this context?

Not visible along their whole length for inspection.

https://www.gassaferegister.co.uk/he...lues-in-voids/

a room sealed, fan assisted boiler with a flue which is hidden behind a ceiling or wall, then a Gas Safe registered engineer will be unable to inspect the appliance.
If a Gas Safe registered engineer visits and is unable to view the flue they will classify the appliance as 'At Risk', which means:
It will be shut off (with your permission)
It cannot be operated again until inspection hatches have been fitted in appropriate places.
Most of the affected systems are relatively new (installed since 2000),

There is no legal duty on the consumer to have inspection hatches installed. However, there is a long-standing legal duty on gas engineers to be able to examine the flue to ensure it is safe whenever they work on your boiler.

Okay, is this just for boiler then? That's not a problem.

I was thinking about the original chimneys, which could now be used
for a gas fire. Mine passed a test meaning no flue liner is needed. I
believe some others do have flue liners fitted. There is no way on
this earth you could get to them without demolishing part of my lounge
wall. I would require a huge compensation package before agreeing to
this, including redecoration of the whole room afterwards.