Gas Logs Sooting

If you have gas logs that have turned black with soot (see Fig. #1 & #2 below), odds are you did not cover the burner completely with the sand and embers that came with your burner (see Fig. #3 below). This important step during installation is commonly misunderstood by DIY'ers because they think they will get more flames and do not understand why it is necessary. So why is it necessary? The sand and embers slow down and spread out the flow of gas and provide the proper air to fuel mixture. If the sand is not there or does not cover the burner tubes completely, the gas burns too rich and produces soot like you see in the example below. Gas logs that burn liquid propane use vermiculite instead of sand because propane is heavier than natural gas and requires a less dense media to burn properly.

Another cause for sooting is what we call "The Poor Man's Gas Log". This is where someone places some fake logs on their wood burning grate and uses their log lighter as a burner. This is essentially produces the same results as described above.

Bottom Line: make sure you use a proper gas log burner system and cover the burner completely with the sand and embers that come with it.

Fig. #1: Gas logs installed with NO sand in the burner.
Fig. #2: You can see that the soot got on the mantel and ceiling as well.
Fig. #3: Illustration showing how sand and embers are supposed to cover the burner tubes completely

Gas Logs Questions and Answers

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Question: I do not really need the heat, and I have a fireplace already,but, the damper is either all the way open or completely closed. can I get that fixed so i can have it open part of the way so all the hot air does not go up the chimney thereby kind of making it silly to have one
Answer: Technically, a vented gas log is supposed to be burned with the damper completely open. Plus, you cannot ever completely close the damper just in case there is a gas leak, so there is a clamp that is included with the burner system that gets attached to the damper to prevent it from ever closing completely. So if you do not really need the heat, then the way your damper operates is sufficient for a vented gas log. Whether you close the damper slightly to preserve some of the heat will not make much difference, you will get most of the heat from a vented gas log radiated into the room from the ceramic in the logs themselves. If you are really concerned about getting heat (which you say you are not), then you should consider buying a ventless gas log.
Question: My daughter has vented gas logs in her bedroom which is about 24x36. It is her primary heat system. Recently we noticed that the ceiling and top part of her walls were becoming covered in black soot. Why would the logs start this and is it dangerous to them. They have a 1 month old that sleeps in that room as well. I have noticed that some of the baby toys that are plastic have the black on them also. I am very nervous about this. Would it be better for them to get ventless with a heatalator?
Answer: Please stop using the gas logs immediately, it is dangerous to use them if they are producing soot. Where there is soot, there is also carbon monoxide, which as you know is a lethal odorless gas. You need to have your gas logs serviced or replaced because they are no longer burning cleanly as vent free gas logs should. Some Heating and AC companies are qualified to service ventless appliances, so use your local yellow pages to call around. Or, you can use the resource on this page to locate a professional who is qualified to service your gas logs: Locate a Gas Log Service Professional.
Question: We are thinking about converting our wood burning fireplace to gas. We obtained 2 estimates from local companies. One company told us that in order to go ventless, we would have to change out entire fireplace, box, chimney insert, basically replace everything. The other company said it would be no problem to convert over and was much more reasonable. We want to make sure it is safe and no fire hazard, not sure which one to believe.
Answer: If you can email me some pictures of your fireplace I may be able to help clarify whether or not you can use ventless gas logs in it. If it is a prefabricated fireplace, the answer will be determined by the owners manual for the fireplace. In order to find the owners manual, we will need to know the brand and model number of the fireplace. To do so, look for a metal label somewhere around the fireplace opening. If you find it, send a picture of that as well. If it is a masonry fireplace, you should have no problem using ventless logs. In either case, email me some pictures and I will help you determine what you have. Email your fireplace pictures to:
Question: I have a set of gas logs in my house. They are after market logs. We want to make sure they are safe to use. House do I tell the difference between vented & ventless.
Answer: If you can email me some pictures of your fireplace and gas logs, I may be able to identify them. Email your fireplace pictures to:
Question: I live in the Nashville area. Do you have any contacts here who can quote me to install a wood burning fireplace? I have no flue, have ventless. I hate it- I smell gas and no oxygen. My kids and I are too sensitive to it, but we LOVE fireplace ambiance. Thanks!
Answer: I cannot give you a contact to install a fireplace in your local area. I suggest you check the yellow pages to find a local fireplace shop. They are going to be the best resource for getting a new fireplace installed. You may also do well by referring to the resources available online at the National Fireplace Institute.
Question: We have a ventless gas fireplace. It is located on an exterior wall of our brick home. The wall on the exterior is on our patio. What would be involved to convert it to vented? What do you think would be the approximate cost? Who should we call if it is a reasonable thing to do? Thanks very much.
Answer: For starters, you cannot "convert" a ventless fireplace to a vented fireplace per-say. You must remove the existing ventless firebox and replace it with completely different type of fireplace that has a chimney or vent. My suggestion is to replace it with a wood burning fireplace. This allows you to burn either wood or gas logs. It is also best for resale value since it allows the potential buyer the same options.

As far as the is all over the place depending on what you decide to do. You should have a local professional to come to your home and give you an estimate. When I sold fireplaces at a retail fireplace shop, the final cost including installation ranged anywhere from $7,500 to $25,000 depending on the complexity of the installation and the finished appearance of the fireplace. We also sold simple to very elaborate hand carved fireplace mantels that could cost as much as $10,000 just for the mantel. So how the fireplace is finished has a huge impact on the cost. The bare minimum would just be a fireplace with no decorative surround...maybe just a brick or tile facing with some wood trim...for a total of about $7500 installed (that is a prefabricated wood burning fireplace with a metal chimney).

I would suggest visiting local fireplace shops. They should at least be able to get you started in the right direction. These are the options you will need to explore. I would suggest you do some research online about the differences between these:

B-Vent (natural vent) gas fireplaces
Direct Vent gas fireplaces
Zero Clearance wood buring fireplaces.

We do not sell fireplaces (although I did for many years in a local fireplace shop). We sell only the gas logs that go into an existing fireplace. So if you like the looks of the vented gas logs you see on our website, they would require you to have installed a wood burning fireplace with a gas line piped into it. Vented gas logs are much more for enjoyment and realism than for heat.

Here is a link to our vented gas logs:

You may also want to use the resources at the National Fireplace Institute website. You can find qualified fireplace installers in your area using their resource locator. Here is a link to their website:
Question: do vented logs without doors remove oxygen from the air....?
Answer: Fire always consumes oxygen. The question is whether or not the oxygen gets replaced or depleted from the home when burning a gas log. When it comes to the depletion of oxygen in a home (or room), the difference between vented and ventless logs is this:

Vented gas logs are burned with the damper open, so just like a real wood fire, a draft is created that draws the exhaust up the chimney and outside your house. This draft creates a vaccuum which sucks air into your home to replace the air that is drawn up the flue. So with vented gas logs, the oxygen that is consumed is replaced by fresh air from outside...thus eliminating the worry about oxygen depletion. The benefit of this sort of combustion is that it does not matter whether or not the gas burns cleanly. This allows gas log manufacturers to starve the fire a bit, which means the oxygen to fuel ratio is not ideal and the gas does not burn completely. The result of this type of combustion is a very lofty natural looking yellow flame that looks much like a real wood fire that produces exhaust like carbon monoxide, carbon dioxide, carbon (soot) and water vapor. Hence the reason the damper must remain open.

Ventless gas logs are designed to be burned with the damper closed, so they must be designed to burn the gas completely (cleanly) so that carbon monoxide does not enter the room. When the proper air to fuel mix is used to burn gas completely, it produces a more vigorous blue flame that is not as realistic as the yellow lofty flame that vented gas logs produce. The benefit of ventless logs is not the appearance, but the fact that all of the heat produced goes back into the room instead of up the chimney. Because the chimney is closed, no draft is created, which means that air from outside the home is not pulled in to replace the oxygen that is spent during combustion. Also, the water vapor that results from burning gas is not vented outside the house either, so a lot of moisture is introduced into the home as well.

FYI: both vented and ventless gas logs cannot be burned with glass doors closed with the exception of one model designed by R. H. Peterson...or with a gas fireplace or gas fireplace insert that has special venting designed for that purpose.

For more information about the difference between vented and vent-free gas logs, read this: Vented Gas Logs - VS - Ventless Gas Logs.
Question: Can ventless logs be installed where vented logs are currently installed for more heat ?
Answer: Ventless logs have limitations on the type of fireplaces they can be installed in. If it is a masonry fireplace, the answer is most likely yes. If it is a prefabricated fireplace, you must refer to the owners manual or consult with the fireplace manufacturer to determine of ventless logs are approved for the model of fireplace you own.

There are also limitations based on building codes in your city. For example, ventless logs are not allowed in the entire state of California and in portions of Texas.

Can you email me some pictures of your fireplace? If so, I may be able to give you more direct answers. Also, let me know the city and state in which you live. Email to:
Question: Can I leave my vented gas log burning for long periods of time - 24 hours plus? Is there any thing that would cause a gas fireplace to "over heat"? We had an extended power outage and I wondered about burning the fireplace for that long of time.
Answer: There may be no issue with leaving your gas logs on for extended periods of time if you have a wood burning fireplace with a Peterson gas log in it. But I cannot say for sure without knowing the type of fireplace and gas log you actually have. Can you email me some pictures of your fireplace? If so, email them to: and I will try to give you more direct advice.
Question: I am trying to determine if the Glow Fire gas logs model 2 A is vented or non-vented. They are 24000 Btu and appoximately ten years old. Please respond to as sone as you can. Thanks.
Answer: Please email me some pictures of the logs and burner system so I can make the determination. Email pictures to:
Question: How much expense is involved in venting a fire place that now has vent-free logs. Can it be done with out replacing the existing logs. Our home has a vent-free fireplace in the living room, and a large vent-free fire place in the family room. The large fireplace also has a blower in it. Thanks SB
Answer: Unfortunately, there is no way to convert a ventless fireplace into a vented fireplace. Ventless fireplaces are not designed to have a vent added to them. Your only alternative is to tear out the existing ventless fireplace and replace it with a vented fireplace. You cannot use a vented gas log in a vent-free firepalce, nor can you burn wood in it. The cost to replace your fireplace with a vented fireplace will vary widedly depending on the location in your home. It can be anywhere from $5,000 to $20,000+.
Question: can you have an electronic ignition for a pilot light on vent free logs?
Answer: Yes, many of the Ventfree gas logs on our site are available with Electronic Ignition. To choose this option, simply view the product detail page of any of the Vent-Free log sets to see if the option shows on the page in the control options dropdown menu. You can also use this link on our search page to find all Ventless Gas Logs with Electronic Ignition.
Question: in nov 1995, i purchased a perterson 30 LP gas logs (g oak) with a wall switch. they were put in the fireplace in the great room--27X42- kitchen,eating area and den. the smoke was so bad tht they even smoked up the dishes and glasses in the kitchen. you could even see the smoke in the room. it was a big mess!!! I finally threw them in the woods. i am now looking forn something that will NOT smoke and thought that the vent-free set was the way to go. not sure since # 9 above talks about soot.
Answer: The fact that your original gas logs smoked can indicate a few things. Because Peterson gas logs are pretty much the best you can buy, smoking is rarely a matter of the burner system or logs themselves, but rather something to do with the fireplace or the installation of the logs. In most cases, the logs are simply stacked too close together, which starves the gas for oxygen and causes incomplete combustion. A poorly drafting fireplace is the second most common problem. A vented gas log will not draft any better than a real wood fire, so if a fireplace smokes when a wood fire is burning, it will most likely smoke with a gas fire. If you have a see-thru fireplace or one that is open on 2 or more sides, it is common that drafting problems occur. Another cause of sooting from a gas log is that not all propane gas is the same quality. Some propane is simply dirty and will cause more sooting. Installing a vented gas log will drastically reduce sooting if the fireplace drafts poorly because the chimney will be closed and you are not dependent on draft. Ventless gas logs also have specific instructions on the placement of the logs so that they do not cause sooting either. However, if your propane gas is poor quality, some sooting may occur...but it will be far less than what you experienced from the vented log set. Keep in mind that you may still experience an odor from ventless gas logs, which is to be expected. Please feel free to call and talk to our gas log experts for more details about your particular situation.
Question: I want to place a gas log into an existing wood-burning masonary fireplace. I only have access to LP. One fireplace store told me I should only install a ventless unit because of the LP or I would have excessive sooting and unrealistic flame and fire. Another store told me it did not matter. My wife and I have a wood fire almost every night and really enjoy a fire and want the gas log to be as realistic as possible. Your thoughts and suggestions, please. Thank you
Answer: After being in the fireplace business for over 25 years and personally installing over 3,000 gas logs, I can say without a shadow of a doubt that "Vented" gas logs are going to be much more realistic in appearance than ventless logs. However, all vented gas logs will create some soot, just like burning real wood does. If they are properly sized and correctly installed, the sooting will be minimal and will not cause any problems because it will go up the flue just like a real wood fire. Some soot will always be present on the surface of the logs as well, which is to be expected and even adds to the realism. Ventless gas logs will provide more heat and will not create soot (if properly installed), but they are far less realistic. They also produce an odor that many people dislike or simply cannot handle, so ventless gas logs are only recommended if heat is the primary reason for thier use. Keep in mind that when you burn wood, soot is a natual part of the process. If your wood burning fireplace is not sooting up your house, then a vented gas log will not either.
Question: In addition to smell, how do propane logs differ from those burning natural gas? After two vented sets, we are really interested in the ventless type,
Answer: The biggest difference between natural gas and propane is the cost! In most parts of the country, natural gas is about 1/2 the cost of propane, so if you have access to both fuel types, natural gas is usually the logical choice, but you should check the difference in price. Natural gas is generally sold by the "Therm" where as propane can be sold by the gallon or pound. Ultimately, to compare the cost of both fuels, you will want to convert the unit of measure to BTUs. So, how much you pay per 1000 BTUs is what you want to consider.

Here are the BTU conversions for both gas types:
  • Natural Gas: 100000 BTUs per Therm
  • Propane: 91500 BTUs per Gallon
  • Propane: 22000 BTUs per Pound

Read more here about: The Cost to Burn Gas Logs

Otherwise, there is little difference between burning propane and natural gas when it comes to gas logs providing you have good quality propane. Natural gas is generally quite pure, whereas propane has less consistency in purity. So the quality of the fuel can vary quite a bit between suppliers. Propane that is less pure (dirty), will tend to produce more soot and smell. Also, propane burns nearly twice as hot as natural gas by volume, the ventless gas logs are ported differently for each fuel type, so they end up producing the same amount of heat. With vented gas logs, the BTUs may be different between natural gas and propane, but the natural gas models tend to burn hotter than the propane burners due to the way the burners are ported and the gas is regulated.
Question: I currently have a Napoleon gas fireplace insert. Its17 yrs old and the mercury switch went on it and I cannot find a replacement or bypass so instead of buying a whole new fireplace insert I thought that I could buy a gas log set and install it in the box myself. The fireplace has a 4" chimney and a blower. It this possible. The inside of the box is 13" by 30" Thanks
Answer: You cannot install gas logs into a gas fireplace insert. Gas logs are designed to be installed only in wood burning fireplaces, or in some cases, a ventless firebox that is factory approved for aftermarket ventless logs. Your Napoleon gas fireplace can only be used with the burner system and logs that it came with. There are no options to change it to burn anything else. The main limitation is the 4" B-Vent and the thin-walled construction of the firebox. Gas logs require a chimney and firebox that is capable of burning wood in order to draft properly and burn safely.

So, either you will need to find someone who is capable of repairing the fireplace, or replace the insert. You may be able to find a qualified service technician using the resources here on our website: Certified Fireplace Installers and Service Technicians.

BTW, the term "gas fireplace insert" refers to a gas appliance that is installed into a wood burning fireplace that converts it into a gas fireplace. Many people confuse this term with the term "Gas Fireplace", which is a completely different type of appliance. so I am not exactly sure which one you insert or a gas fireplace. Can you email me some pictures so I can see what you actually have and possibly offer more advice? Email to:
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