Ventless Gas Fireplaces.

Ok, I give. The byproducts of burning natural gas include carbon monoxide, PCBs, particulates, and so forth. Yet, we have these nifty gas fireplaces that have no vents. As the stores that sell them will quickly tell you -- no vents are needed, there's no exhaust.
Huh? It's a simple reaction -- the byproducts must go somewhere. So what's the deal with these things? Are they just that efficient? Is the exhaust just so minute that it's not worth noticing? How do these things work?
James
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Back to chemistry class. Natural gas is mostly methane CH4 Burned properly you get H2O and CO2 . The modern ones include CO detectors that shut it down if the CO gets going. Under normal operation it is not a problem.

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Although predominantly methane (typically 92%-95%), the actual chemical composition of natural gas varies depending on its source and processing and includes several other items in small to trace amounts. When it burns the byproducts are primarily water vapor and carbon dioxide but also a variety of other things including carbon monoxide, nitrogen oxides, particulate matter (such as soot/creosote), and pipeline contaminants. Even if the equipment is functioning as designed, these items are being burned along with the methane.
Obviously, these are for the main part negligible -- they're just not a primary factor and this is why natural gas is considered to be a "clean" fossil fuel, if not the cleanest altogether. I'm not one of those types that are down on NG by any stretch -- if we gotta use fossil fuel, I'd really rather use that one among the alternatives.
It's good that most models include a CO detector but that's not the only exhaust issue here. It's just difficult to believe that these units, even when operating properly, do not contribute to air quality issues -- especially since they're run in cooler weather when houses are sealed up fairly tight. (I'm aware they have oxygen detectors to ensure they do not take too much.) I suppose my real question is just what makes these any different than a furnace or other NG appliance that it's ok to vent them right into the room?
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Frankly I would not have one for regular us in my home, and I generally advise that, but I don't believe current models are a serious health hazard. Those kero burners really worry me however.
BTW I do own one and I keep it as a backup for a long term winter power outage. It is not even hooked up, but I have all the parts and tools ready to hook it up if I need it.
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Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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They can....it depends on the home. Some people will swear by them, and swear they have a tight home. Most have a tight home, but not near as tight as they think. Those are the ones that have no problems with the units.

After sitting though 2 hours on this one subject yesterday as part of our continuing ed for the state licence, I can assure you, a tight home is not a sealed home...

The limits on those are at 21%...and we need a min of 18% to live...its just a bit freaking close IMO..

The amount of fuel used, the combustion process, and the amount of harmful products generated in relation to the gas used.

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I realize that no home is really THAT tight. :) They're certainly more tightly sealed up during the winter months than others though. I know some just run it as a "feature" and turn it off when they go to bed sort of thing, but others put it on a thermostat and let it do its thing. My folks have one and I'm assuming it's a decent unit as they dropped a pretty bundle on it when they bought it. I can tell when it's on just by entering the house -- I smell it just as well as the oven. I dunno -- just seems to me that the things gotta contribute to air quality issues.

This is true. :)

This is interesting -- you say the combustion process is different. How so?
I'm guessing that the gist of your class was that conventional wisdom dictates these things are no problem?
James
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Well..burning gas is burning gas, until you get to the part of the by-products. A furnace, as used in the other example, will produce much more in the way of harmful contributions to the air, in the home, should the exhaust be venting indoors, due to the sheer amount of fuel being used, and the way its being burned.

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I'm going to guess that the furnace produces more because it burns more to do its job -- correct? What's the differnece in HOW it is being burned? Aren't they both pretty much using a tube with holes that is lit by a pilot?

I'm very much of the same opinion.
James
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Whoops..hit send too soon...

Actually, they suggested that we shy from installs, unless the homeowner understood that they can:
Kill, and in some cases, soot up your home in ways you never thought possible...and that we follow code to a T, and make sure that we understood all the loopholes that could create an unsafe condition.
Personally, I would much rather prefer a vented model.

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JNJ wrote:

just my opinion, go with a direct vent. i would not have vent free.
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Ventless heaters keep coming on and off the market. They can be very efficient since you are getting all the heat. Yes, you are breathing all the byproducts. You will find that the water vapor produced will steam up the windows all the time and sometimes cause rusty drywall nails in the ceiling. When other chemicals are used in the house, such as a small paint project, the smell will be greatly magnified. Some people have headaches when the furnace is in use. These are some of the costs of not venting.
PS. Same goes for any gas stove or oven. It's a good practice to crack a window in the kitchen when using them. Even a small vent is quite helpful.
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house with my unvented LP gas fireplace. Any idea why? It's a 6 year old house, well insulated. I do leave a window near the FP open slightly all winter as recommended by the manufacturer. The FP is larger than we need so we don't run it for very long at a time as it gets too hot in the house. Might this be the reason we don't have a vapor "problem?" ==
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This is Turtle.
The ventless models get away with no vent because the panel Ray type burns at about 3,000 F . All the carbon is burnt up and you have no carbon to make CO with. Now it can burn up all the O2 and be bad too , but they have sencer on them to turn it off it this happens.
When gas or anything else burns at 3,000F there is nothing left to make anything else out of the vent vapors.
TURTLE
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<...previous quote snipped...>

Ha ha! That's a good one!
--

Larry Wasserman Baltimore, Maryland
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Nope!
Since providing "excess" air to a ventless fireplace doesn't reduce the efficiency, that's how they burn gas. The result is that the health hazzard isn't CO but oxygen depletion. The units all have the pilot light positioned so that if the O2 levels go doen, the thermpile gets cold and the unit shuts down.
I have a digital CO detector very close to my ventless unit. It has never gotten off ZERO because of the ventless burner. (It has responded to cooking on my ELECTRIC stove.)
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Actually, it simply shuts the unit down....wired in with the gas valve..

Then its crap. Most residential units will not get off zero till the actual ppm is near 50...a good Fluke, or UEI CO handheld will show you what the others wont.

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YEP! Do your research -- the gas piped into your home is not pure methane. It is typically around 92% methane with the remaining 8% consisting of a variety of other substances, including some contaminants depending on the source, processing, and transport. This is a well known and documented fact -- documented even by some utility companies right smack dab on their web site.
The point is that the burning of gas within a closed space affects air quality. How badly depends on a variety of factors such as placement, gas, efficiency of the burning mechanism, and so forth. Whether the affectation is minimal or significant enough for concern is open to debate.

It would have to be a fairly well closed up room for the oxygen levels to deplete. As we discussed elsewhere in this thread, these detectors have a threshold that is awfully close to the minimum levels we require to survive. Not 'xactly what *I* like to hear, but if it works for others.... :)

Hmmmmm....
James
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