Q&A Top vent or Direct vent fireplace?

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New Member
Staff member
Nov 27, 2012

Hello Mr. Issod (Craig!), thank you for providing this service! I've recently fired up the top vented natural gas fireplace in my home (for the first time) and it has an incredibly terrible odor of rotten eggs/exhaust. This odor actually makes me ill to the point of headaches, confusion, vomiting, and passing out (has happened twice, now). The gas co. detects no dangerous levels of carbon monoxide, so apparently it's quite safe, just makes me ill! I've done a bit of research and would like to know if I'm on the right track: Top vented fireplaces (gas), non air-tight are commonly "smelly" and with use of blower, fumes are even worse. Is this correct? I have also been told by a gas tech that top vents are never supposed to be used on a constant basis, but rather just occasionally, and for brief time periods with windows open. He said top vents should never be installed in newly built homes, primarily due to negative air pressure problems. Is this correct? These last two questions are the most important because if this is so, I'm seriously thinking of having my new, albeit unusable, fireplace removed, and a direct vent, air-tight (sealed) unit installed, though I know the expense could be great. I would be most grateful if you could tell me if my information is correct, and if you would advise me to install a direct vent. By the way, the top vent does have outside air feeding it, and no gas leaks. All seems to be in working order except that it gives everyone who has come into the house a headache, and makes me quite ill. Thank you for any help :)


Something must be wrong...

Let's go thru the concerns one by one.
1. Top Vents are not for full-time use - seems strange since your furnace and hot water heater are also top-vents. I never heard this before....and also never heard about the windows needing to be open. Sure, if your house is super-tight and the unit needs combustion air, then you may need to crack one. That said, NO fireplace is made for a 100% duty-cycle...
2. The smell and headaches - First, I'm sure that you are aware that the first 10 hours or so of break-in will produce smells as the paint and machine oils burn from the stove. However, the rotten egg smell is typical of unburnt gas, and seems to indicate a problem. I recently had a customer complaining about the same thing with a vent-free fireplace. He had the gas company and an installer check it out and they gave it an OK. When I got it back to my shop I hooked it up and discovered a gas leak in one of the tubes leading to the burner. It gave me a headache in 5 minutes.

It is also possible that, for a number of reasons, the chimney is failing to updraft. This would result in the spilling of exhaust gases into the home. This may be happening only on an occasional basis, which explains why the gas company may not have found the problem. Many units have a safety spill switch which does not allow this to happen (the unit shuts down). Ask your retailer or the maker of your fireplace if this unit has one.

Negative pressure in a home can be a problem, and it's one that has not been properly addressed by current building codes. Direct vent units are definitely preferable and less likely to have this type of problem
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