I have a victorian fireplace with a modern gas fire installed. The fire place has a hatch at the top to open/close the chimney, which the fitters have connected to a wire to force it to be fully open constantly. However, it loses a lot of heat through this. I believe it is partly ventilated from underneath. How much should this kind of hatch be open? can I close it completely? Can I close it and have a CO monitor? Surely as long as this is OK there is nothing to worry about?

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    I presume that if the flue is "forced" open, then you have a vented fireplace system, is this correct? – Aaron Dec 13 '11 at 22:29
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    @Aaron Forgive my ignorance, but aren't all fireplaces vented? – Paul T Davies Dec 14 '11 at 8:54
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    Is it a fireplace unit or a log set or something else? I know they make ventless log sets (they burn very efficiently) so that you can use them in a "nonfunctioning" fire place. – Aaron Dec 14 '11 at 12:05
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    Is the control for the flue accessible? – Tester101 Dec 14 '11 at 14:34
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    With any gas appliances or fireplaces in your house, you should have at least one CO monitor regardless. – gregmac Dec 14 '11 at 21:39

Your flue should always be open when the fireplace is operating. It is a fire and smoke risk to close the flue while the fire is lit.

When not burning, the flue should be closed to prevent heat loss.

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    I assume in all this talk, by "closing the flue" people mean closing the damper to seal the flue? The flue is the interior of the chimney that the smoke rises into, right? – glenviewjeff Oct 28 '16 at 1:04
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    @glenviewjeff - technically yes, it's a damper. And the flue lever attaches to that, which is what I suspect the problem is: that linkage is broken. – Mazura Jun 8 '19 at 2:22

In some jurisdictions the damper and top hatch must remain partially open at all times when you have a gas fireplace.


the fitters have connected to a wire to force it to be fully open constantly.

The only reason I'd do that is if it didn't stay open by itself. Even if it seems to, once it gets hot enough it might close. I would not use that fireplace with the wire removed, until I've verified that the flue is cooperative.

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