On Wed, 14 Oct 2020 08:15:27 +0100, Brian Gaff \(Sofa\) wrote:

Why would I need three and why a heat alarm ...

Less chance of false alarms with heat alarms in/near kitchens.

... and a co2 alarm?

CO ...

In the room with a gas boiler in case the professional servicing it
fups up the combustion settings and damages the room seal allowing CO
into the room.

In the room with a woodburner/stove, damaged seals allowing CO into
the room. A stove/wood burner needs a decent free air supply, without
which the draw for the chimeny might not maintain a negative pressure
in the stove. Wind direction dependant...

--
Cheers
Dave.