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Are ventless fireplaces really that bad?

jadmacjadmac Posts: 1Member
I've just moved into a new house and I'm currently looking into getting a new fireplace. There's no chimney so I'm liking the idea of a ventless fireplace, but there seems to be a lot of concern about them online. For example, this site says they are potentially hazardous:

But surely if they are fitted with oxygen depletion sensors and catalytic converter it's relatively safe?

Views would be appreciated, cheers


  • ratioratio Posts: 1,812Member's relatively safe?
    I think that about nails it.

  • Jamie HallJamie Hall Posts: 9,746Member
    "However, carbon monoxide gas that is odourless is a real danger to gas fuel users, which is why its good to know that this model by ... comes fitted with an oxygen depletion sensor, which shuts the pilot off before oxygen drops below a safe level"

    Quoted from the review.

    May I respectfully point out that carbon monoxide -- which is deadly in high concentrations and none too good for you even in low, is not the same as oxygen? All the oxygen depletion sensor will tell you is that you are about to suffocate. The carbon monoxide -- which is inevitable with an open flame -- is still there.

    For reasons which pass my understanding, these things are permitted, but not usually in sleeping areas. I myself wouldn't have one on a bet anywhere inside, unless I had a lot of ventilation in the house.

    Is there some very good reason you can't use one with proper venting?

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Tim McElwainTim McElwain Posts: 4,181Member
    There has never to my knowledge been a carbon monoxide issue with any of these units. They are all required to have an ODS and if anything they may sometimes be a nuisance as they shut off prematurely. They are designed to shut down when oxygen level reaches 18% (normal is around 20%). I have worked on hundreds of these and most are pretty reliable. Just make sure whoever installs it is reputable.
  • DZoroDZoro Posts: 663Member
    Had a elder gentleman/friend of mine who used one. AGAINST MY WISHES, but he was stubborn, couldn't tell him anything. I'd usually stop by just to say hi when I was in his area. He is no longer with us due to that POS. Family didn't want to stir anything up, and asked for no autopsy, but that is what took him to his grave....... I now carry a personal CO detector on my side daily.....
  • newagedawnnewagedawn Posts: 549Member
    they are safe, if given enough free space for combustion and are not considered a primary heat source
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • jimctjimct Posts: 9Member
    I am not a pro just an owner. There is one in my lake house. I only use it with a window open. It triggers sinus issues when running. If I retire to that house it will get replaced with a vented gas fireplace. When I rent to tenants, I have the fireplace disconnected.
  • Big Ed_4Big Ed_4 Posts: 1,097Member
    If it all goes wrong , I rather see it vent outside ..

    I have enough experience to know , that I dont know it all
  • SteamheadSteamhead Posts: 12,648Member
    jimct said:

    It triggers sinus issues when running.

    That's reason enough to get it replaced NOW. One of your tenants might just have some wrenches with him.

    Our company doesn't touch these things, except to disconnect them.

    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • BrewbeerBrewbeer Posts: 547Member
    When I put one in my house, I went with a vented unit.
    Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread:
    System Photo:
  • FranklinDFranklinD Posts: 387Member
    I have a ventless heater in my garage, and that’s about the only place I’d EVER use one. I also followed the install guide - to the letter - regarding ventilation air and total free air volume of the “room”. And still, I will only use it when I’m actually IN the garage, I have 2 CO detectors out there (one high & one low, height-wise), and I have a fan-assisted vent system for when I’m working on vehicles in there.

    I think putting a ventless gas heater of any kind inside of any living quarters is downright loony.

    If I could find a *relatively* inexpensive used NG 90%+ efficiency hot air furnace, I’d go that route instead (I don’t want to have to use b-vent...I want sealed combustion with pvc intake & exhaust)...maybe this summer I’ll have more luck finding one locally.
    Ford Master Technician, "Tinkerer of Terror"
    Police & Fire Equipment Lead Mechanic, NW WI
    Lover of Old Homes & Gravity Hot Water Systems
  • GWGW Posts: 3,299Member
    Jamie true yet anything in the air will reduce the o2. Too much stuff and the unit will stop. I’ve never installed one but I would, they seem to be well designed. And they’re not supposed to be used for normal everyday use. At least here in MA
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • HenryHenry Posts: 859Member
    We do not permit them in Canada! There was one at the Natural Gas Technologies Center when I was in charge of the lab. It was removed for obvious Co2 and Co problems.
  • SuperTechSuperTech Posts: 663Member
    As an HVAC service technician I take carbon monoxide and combustion analysis very seriously. Whenever I see one of the ventless fireplaces in use or even worse a kerosene heater I will start up my Testo 320 outside in the fresh air and make sure I point out to the homeowner how many parts per million it is detecting.

    Homeowners have a tendency to put too much faith in whatever they are using as a CO alarm.

    I've had quite a few try to insinuate that my Testo, which I baby like it's my firstborn, isn't working correctly because their detector never went off.

    Just get some pet parrots if you have any doubt.
  • NY_RobNY_Rob Posts: 1,351Member
    edited February 2018
    ^ you might be better of with a Sensorcon Inspector for low indoor levels of CO vs. your CA. And, they're ready to use in 10 seconds unlike the CA.

    Quite a few of us have them... excellent units!

  • SuperTechSuperTech Posts: 663Member
    Thanks Rob. I have been thinking about getting a personal CO detector. The only thing I like about using my Testo is that when I'm done with everything I can print out the results. Including ambient CO testing. But the unit you suggested would prevent several unnecessary trips outside to start up the Testo in fresh air.
  • lchmblchmb Posts: 2,877Member
    interesting part..if you google it, they say their have been no reported death's due to a vent free unit which everyone hates... yet how many deaths from improperly installed vented units?? Maybe we are so worried about one we forget to pay attention where we should...
  • Big Ed_4Big Ed_4 Posts: 1,097Member
    How many times you find it's the gas stove or oven tripping the detector ..
    I have enough experience to know , that I dont know it all
  • GordyGordy Posts: 9,009Member
    Remember the kerosun kerosene heater rage. Burning in the living rooms all across the snow belt.
  • Big Ed_4Big Ed_4 Posts: 1,097Member
    Yes when oil prices passed $1 per gallon ...
    I have enough experience to know , that I dont know it all
  • DZoroDZoro Posts: 663Member
    The sensorcon is a great instrument, don't leave home without it. Amazing how much CO it detects just from starting the truck and backing it out of the garage. The CO is there for hours. In our area if the gas company finds a ventless unit they red flag the home. Have never actually seen them turn off the gas, but they do inform to the owner that it must be removed.
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