Ventless or Vented gas logs?

How do you tell the difference between vented and vent free gas logs? I’ve looked on the metal tags but don’t see any indication of which it is. Thanks!


Good question.
This site may hold the answer if you look through the tech stuff, though they do not really directly answer the question on this page for some reason.

They do explain whats in them.

I don’t spend much time trying to figure it out during an inspection if it’s a traditional fireplace with a damper (it could be either type). In that case, I say this:

“We were unable to determine if the gas log set is designed to be vented or un-vented. This is important, because if it is the vented type, then the chimney and damper must be open to discharge products of combustion. Carbon monoxide is a deadly gas! You should obtain documentation about the gas log type and operate the logs according to the manufacturer’s instructions. Also, clearances to combustible materials are determined by the manufacturer of the gas logs, so you should understand their specifications regarding fire prevention as well.”

Thanks for the replies. Joe, I will definitely be using that statement in future reports.

One quick clue is if there is wool (“glowing embers”) under the logs. If so, that’s a vented set. That being said, you know some nut will buy some glowing embers and put them around his ventless logs :roll:.

I have also heard that the more realistic looking sets are vented and that the vent free ones are smaller and cheaper looking. Any truth to that??


There is no such thing as a ventless fireplace. There are fireplaces that vent through chimney…and there are fireplaces that vent directly into the home, adding moisture and other gases that sometimes will include varying amounts of carbon monoxide.

In addition to the venting of moisture and other gases, the fire competes for the breathing air of the human occupants and as less air becomes available…the more yellow the flame, the more incomplete the combustion, and the more carbon monoxide.

Wanna kill a client or maybe a couple of his kids? Be silent about the deadly condition presented by his so-called “ventless” fireplace and then advise him to add insulation in the attic and tighten up his house to save energy.

I think so. I’ve always felt a vented set is more realistic. I bought a fairly expensive ventless set for my own home and wish I would have kept the vented.

I have it easy in Minnesota, as ventless are banned. If no vent to the exterior, it gets written up!

Do you have any reasoning under that code.
I would love to use it next time I warn people about CO.

As far as “reasoning” goes, the only reason I need is the State of Minnesota say’s “NO”.

The (my) assumption (other than what James stated above) is that safety devices fail, if they even worked properly to begin with, and winters in Minnesota being what they are, the risk from CO poisoning is too great, as people get very creative on totally sealing their homes for the winter. Remember, most homes in MN are older structures, and energy efficienty is difficult at best. There’s a reason 3M headquaters is in MN.

Yeah ,most of us know that stuff ,but I did not realize there were laws against them any where.

Yes the only reason you need is code ?
“No brain ,No pain”:neutral:

“Cop out” since it is always best to state a real reason in the physical world,otherwise we would all just obey every law ,and never question anything.

Plus ,since when are we code Inspectors ?

I never mentioned “code”… you did.

You cannot purchase one in this state, or have one shipped to this state. The only ones you will find, are pre-ban, or someone that purchased and transported it into the state themselves. Basically, it is a non-issue for me. I think I have written up two in the last four years. Those were in older “vacation” cabins.

There are actually a handfull of states in which they are banned. I’ll see if I can find the list, and post it tomorrow.

Do you have any data to substantiate that claim? Let me go ahead and answer for you. NO.

Here’s a some more objective information.

Ok cool, because I would love to see it in code.

I would also love to see the explanation behind the code so it feels like an official reason to be cautious.

Even though we do not really use the code ,it sure does make a solid justification for our reasoning in the report comments.

It’s odd that Minnesota does not outlaw kerosene heaters. I guess they will get to it later.:roll:

Well as Souchery says-" Minnesota, the state where nothing is allowed"

BTW- According to the CPSC, there are no deaths associated with the use of vent free fireplaces that are equipped with and ODS

Problem #1: The burning of natural gas produces large quantities of water (1.5 gallons for every 100,00 BTU’s of gas burned.)

Where the hell did the mold come from?

Problem #2: discharging combustion gases directly into the living space of the house is only theoretically “safe”!

The assumption is that the appliance is utilized in a poorly constructed building that exceeds the minimum building airflow standard (ASHRAE 62 – 89). Any attempts at weatherization by a professional or the homeowner may result in unsafe carbon monoxide levels in the house.

To start with, there is insufficient building envelope leakage to let the carbon monoxide out, insufficient leakage to allow dilution air into the living space and insufficient leakage for adequate makeup/combustion air resulting in elevated carbon monoxide as a result of incomplete combustion. But then we all rely on that oxygen sensor the appliance has (heaven knows this thing will never fail)!

Weatherization programs pending ratification by the House of Representatives prohibit unintended combustion appliances with the exception of gas ranges and ovens. These appliances will be tested during the process and appropriate ventilation will be required in accordance with test results.

Install them now and you’ll have to uninstall them later. No weatherization work can be performed (not one caulked window) on a house without removing unvented fireplaces without assuming 100% liability for future performance of this appliance and the maintenance of adequate ventilation.

As Joe looks for “just the facts”, take a carbon monoxide test after you exceed the standards of practice by lighting fires in the fireplace!

I have measured CO and guess what?

1-2 PPM or better.


You modify my statement by removing half of what I said, and then challenge me to “substantiate” your modification.

I didn’t realize this was one of those moronic “NFE” threads. Sorry.

Even the manufacturers of these inaccurately named “ventless” gas appliances will warn the consumer to keep a window open while operating…like someone in February who needs the extra heat is actually going to open a window when they turn on their “ventless” device. LOL

As for the number of folks who have died as a result of carbon monoxide poisoning in in homes that they have had tightened…or did themselves…without knowing to add mechanical air to keep their gas appliances from backdrafting…there are many. Google them, yourself.

Home inspectors should be warning their clients about these devices and particularly should be educating them to understand that they are not “ventless”. They will vent whatever they do not combust…and (especially when connected to LP) will pump in pints of moisture by the hour.

Do you warn you clients about the use of their “ventless” gas range and ovens?

I doubt it.