fire sensor

Been researching for some time but there don't seem to be any definitive answers out there for this one. I even contacted Texecom directly and they didn't want to give advice, instead stating I should ask an installer. In short, I have a unvented hot water cylinder in the loft, plus two in-line...

What the right sensor apart the carbon monoxide to install on the utility cupboard where we have boiler switch board and washing machine. Thanks