Hugo Nebula wrote:
Martin Bonner wrote

The chimney is to let smoke/fumes out. The vent is to let fresh air in
(so that smoke/fumes don't come into the room and poison you).

Strictly speaking, it's not. The fire would use all the oxygen in the
room and would then smoulder until such time as the emergency services
discovered the bodies of the occupants and the incoming oxygenated air
would restore the fire. There would have to be a blockage, a
downdraught, or the flue not drawing properly for the gases to come
back into the room. The air inlet is to allow enough replacement air
so that the occupants can breathe as well.

Aren't you over simplifying just a bit? Does a smoke bomb test
always work, or is there sometimes spillage? Besides the
proportion of room air which enables combustion, there is a much
greater quantity of air which has to be available to be warmed
and rise up the chimney carrying the products of combustion.

Houses used to be much more draughty, and the air simply found
its way in. Now everything is sealed, proper provision has to be
made.

I recall my parents had a pair of telescopic plastic vents which
popped up out of the floor near the fire, and drastically reduced
the freezing draught under the door.

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.