Gas Heater flue

[DBACT]

I have a Brivis Buffalo 120 heater located in an underhouse area I would like to build into a utility room.

Can I add a extended flue to vent it to an outside wall? Is it possibly to box in the heater?

The obvious concern is asphyxiation, eg from a gas leak. Is this a risk? Should I get a canary?

[Bloss]

My Brivis is well under the house (for moer than 8 years) and has a 50mm pvc pipe venting steam (ie: water, and that nasty CO2) to the outside over about 3m distance - angled slightly upwards. There is separate drain at the bottom of the unit for condensate to flow through and out of the heater.

Might seem unnecessary, but I think that regulations would make it a licensed plumber/ gas-fitter job and that would remove uncertainty.

[wonderplumb]

Mate I would consult an inspector or someone from the utility to have a look at it for you. It MAY be able to be done, depending on the size of the room, ventilation, MJ output of the heater etc.
The utility would be your best bet.
It will have to be done by a licensed plumber