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  1. #1
    David Edens's Avatar
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    Default Ventless Fireplaces Vent How?

    I am at a loss to explain how a ventless fireplace works when combustion is taking place and other "similiar" prefabs have direct venting or the tradional flue. Could someone give me a clue. Of course, I usually recommend a carbon monoxide detector to any gas log fireplace! Thanks

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  2. #2
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    Default Re: Ventless Fireplaces Vent How?

    The industry position:

    www.FireLogs.com - Frequently Asked Questions (FAQ)

    A good short article for clients re: the safety issues:

    Vent-free gas logs not intended for continuous heating Chicago Sun-Times - Find Articles

    Some anecdotal evidence
    Sweep's Library - Vent-Free Product Letters

    A good case study of chronic CO poisoning (This is you brain on CO):

    http://www.pubmedcentral.nih.gov/pic...3&blobtype=pdf

    Last edited by Michael Thomas; 09-27-2007 at 12:05 PM.

  3. #3
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    Default Re: Ventless Fireplaces Vent How?

    Quote Originally Posted by Fritz Kelly View Post
    Pretty simple really, they use oxygen from the living area and vent carbon monoxide and moisture into the living area.
    Yep.

    If burning properly, there is no CO output,
    Someone will need to explain that one to me.

    There *is a reason* ventless gas logs and fireplaces have metal tags attached to them which state 'open doors and windows to allow adequate ventilation' and/or 'use only in adequately ventilated rooms'.

    I think they are a really bad idea but allowed in most areas.
    I agree there.

    Question: Where do ventless gas appliances vent to?

    Answer: To the inside of the house.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
    Randy Brooks's Avatar
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    Default Re: Ventless Fireplaces Vent How?

    David,

    Describe these units as “Lung Vented” appliances. This will usually start a spirited stream of questions. Honestly, this is a quit literal description of the products.


  5. #5
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    Exclamation Granny's question for yer

    From the Beverly Hillbillies, Granny told a suspected Yankee, "yer either fer us or agin' us!"

    No middle ground on these appliances. VF are tested and listed to ANSI Z21.11.2b. Look on the attached metal tab to ascertain whether VF or vented or both.

    Ventfree/ unvented/ nonvented/ventless/ lung vented appliances burn similarly to other hearth appliances. They have atmospheric injection burners with primary aeration at both the burner venturi and the ODS pilot and, of course secondary aeration (ambient room air).

    Fritz wrote" they use oxygen from the living area and vent carbon monoxide and moisture into the living area. If burning properly, there is no CO output, just like any gas applaince that is operating properly." Sorry Fritz but this is a major misconception.

    When you burn methane in a stoichiometric mix (perfect combustion), you get heat, light, carbon dioxide, and water vapor. However, there is no such thing as perfect combustion. There is some degree of incomplete combustion with every combustion appliance. Therefore, you will get some CO. ANSI sets standards for allowable CO air free for the following appliances:

    ventfree- 200 ppm
    Cat.1 furnances, boilers, and water heaters- 400 ppm (stack)
    Direct vent gas fireplaces-25 ppm
    gas oven- 800 ppm

    And you just though it was the tryptophan from the turkey making everyone sleepy on Thanksgiving! Most heating appliances burn with a non-luminous blue flame and therefore tend to burn cleaner. I said tend. You don't know unless you run a combustion analysis. Hearth appliances by their very nature burn with a yellow or luminous flame, which means some incomplete combustion. The hearth appliance flame should have blue bases with yellow tips. That yellow is caused by carbon particles incandescing much like a light bulb filament. That's soot. Where there's soot, there's some CO. You don't know until you test with an analyzer.

    VF are tested in a lab to burn clean enough if you follow the rules, install them to the manual, esp. log positioning, and properly maintain them. I have never found a VF appliance in the field that was properly maintained. Never. Also, there has never been a credible field study in vivo of how these units are actually performing in homes. The reporting structure in the country is a joke so don't assume low incidence rates quoted are gospel. Someone at the scene has to report a death or injury as CO related to trigger the CPSC.

    HTH,
    Bob

    Keep the fire in the fireplace.

  6. #6
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    Default Re: Ventless Fireplaces Vent How?

    Quote Originally Posted by Fritz Kelly View Post
    Sorry, I meant to say they vent Carbon Dioxide to the interior.
    .........
    By the way, a gas kitchen range is an unvented appliance. Where's all the bias against those?
    Good point and thanks for the honest correction regarding CO2.

    I have had a 30,000 BTU wall hung ventless gas fired heater in my kitchen for the last 10 years with no problems. I have measured it repeatedly with my Monoxor and have never had a reading above 0-1.
    We use it as supplemental heat on cold Wisconsin mornings. At 100% efficiency it's a no brainer in our pre 1900 farm house. It has a ODS(oxygen depletion sensor) that would shut it down in the event of a failure.
    When I inspect ventless logs and heaters I always recommend a CO detector in the home in the interest of additional safety, make sure they are not in sleeping areas and recommend that the manufactures instructions be obtained and followed.

    Note:Not all jurisdictions allow these so HIs need to be aware of local requirements.


  7. #7
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    Default Re: Ventless Fireplaces Vent How?

    Quote Originally Posted by Fritz Kelly View Post
    Jerry, the reason for opening a window is for combustion air, not to vent the byproducts of combustion.
    I thought it was for 'both', and, yes, 'mainly' combustion air, but I also thought it was for the unvented aspect too.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  8. #8
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    Default Re: Ventless Fireplaces Vent How?

    This is kind of like sucking on a car exhaust, isn't it?
    I can see these unvented appliances in an old leaky farm house, heck I grew up with unvented space heaters and I suffer no ill effects, and I suffer no ill effects, and I suffer no ill effects
    I can still remember the odor and the staining on wall paper, etc. inside homes with these heaters, can't be good for you. Of course I live in the DFW area that has one of the busiest airports in the country and I spend several hours a day on the freeways behind millions of other cars. But, I don't want to invite the excess noxious chemicals into my home.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  9. #9
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    Default Re: Ventless Fireplaces Vent How?

    Can somebody explain to me the benefits of having a fireplace of any kind in their home?

    Jerry McCarthy
    Building Code/ Construction Consultant

  10. #10
    David Banks's Avatar
    David Banks Guest

    Default Re: Ventless Fireplaces Vent How?

    Quote Originally Posted by Jerry McCarthy View Post
    Can somebody explain to me the benefits of having a fireplace of any kind in their home?
    Bear skin rug. Bottle of wine. Get it now?


  11. #11
    Ed Voytovich's Avatar
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    Thumbs down Re: Ventless Fireplaces Vent How?

    The use of unvented gas fireplaces or heaters should be discouraged by inspectors who understand the possible negative effects of their operation in a cold climate. The potential for introducing unwanted carbon monoxide into the living area is certainly a disincentive to having these appliances in the home, but the addition of a large amount of moisture to the indoor air is an absolute certainty. Excess moisture can condense on windows or, even worse, it can be driven by positive pressures inside the house into attics and wall cavities where it can condense and allow mold and rot to develop. Consider adding language to your report along the lines that moisture created by unvented combustion appliances inside the house can condense and cause potentially extensive damage before any sign of it becomes visible.


  12. #12
    Ed Voytovich's Avatar
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    Default Re: Ventless Fireplaces Vent How?

    By the way, a gas kitchen range is an unvented appliance. Where's all the bias against those?[/QUOTE]

    This is a gray area the size of a pod of whales.

    In a capacity other than that of a home inspector I have tested numerous gas ovens. The undiluted flue gases at operating temperature vary from under 25 to over 2000 (at which point I pull my monoxor out ASAP). Enough is enough.

    Manufacturers describe permissible limits in a range of terms that go from the reasonable to the hilarious.

    Stove top burners are doozies too. An unimpinged burner may have low- to no CO. When you put a pot of cold water on it the CO can spike so fast that you cannot get your test instrument out before you see a very high number.

    What's an inspector to do?? At the very minimum, I recommend that my clients install and use a range hood equipped with a variable speed motor and VENTED DIRECTLY TO THE OUTSIDE. This spot ventilation should used whenever the range is operated.

    See BPI - Building Performance Institute Inc. for one set of standards. They're in the Building Analyst Standards on the Contractor page.


  13. #13
    Brandon Chew's Avatar
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    Default Re: Ventless Fireplaces Vent How?

    Quote Originally Posted by Fritz Kelly View Post
    By the way, a gas kitchen range is an unvented appliance. Where's all the bias against those?
    It's the combination of the CO load into the room and the duration of exposure that makes it lethal. The load is a function of the CO ppm being generated and the size (BTUs) of the appliance.

    In normal use the gas range/oven doesn't have that lethal combination ... but cooking a turkey and all the trimmings on Thanksgiving starts to push it. It's a good thing we don't cook meals like that every day!

    However, trying to heat your home (or supplement the heating system) with the oven in the winter does kill people. Every winter you'll find stories in the newspapers of some major northern cities were people were doing that and got sick or died.


  14. #14
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    Default Re: Ventless Fireplaces Vent How?

    "By the way, a gas kitchen range is an unvented appliance. Where's all the bias against those?"

    The oven and range are used for cooking, 'while attended' as they say.

    The unvented gas fireplace/log set is used for 'heating' in many areas, and is used for more extended periods of time.

    We have a VENTED gas log set and use it on cool nights, no bear skin rug, be we sit together in front of it relaxing and enjoying the fire.

    Of course, being as it is vented, it produces some, but not much, heat. We can feel the heat it produces out to about 6' - 8' in front of the fireplace, of course, though, the ceiling starts at about 8'-6" at the fireplace wall and goes up to 14' at the peak, so some of the heat would be rising up to there too.

    Oh, and no wine either.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

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