vent free gas logs

[MasterPlumbersKeymaster]

I recently inspected a home for mold, but I think I’m finding soot instead. Detected a slight natural gas odor upon entry and lab results show that the black particles we removed from the walls are not mold. Most of the substance seems to cling to walls over framing members. I advised client to call utility co and report leaking gas, to be aware of potential CO threat, not use gas fireplace and ventilate the house asap. Gas co man found “small” leak in the pipe at the gas log, but advised the homeowner that natural gas cannot cause soot.
Here are my questions:

Wouldn’t soot (elemental carbon) be a natural byproduct of improper combustion?

and

Could gas leaking into the “firebox”, but away from the intended point of combustion cause incomplete combustion?

and

Why doesn’t this gas appliance require venting to outdoors?

Any help/suggestions would be greatly appreciated!

[mikeinpaParticipant]

The soot,or carbon particles you are finding may be caused by the flame burning uncharacteristically, possibly from unusaul drafts maybe ceiling fans,chimney drafts or return air ducts also a by-product of gas combustion is water vapor causing humidity or excess moisture, or the logs may not be placed correctly as spec. by manufacture ,log set may need inspected for proper combustion or cracks in logs ,vent free products use the oxygen in the area in which it is used most all units are equipped with a oxygen depletion sensor shutting off if not enough combustion air is present.

[SelgasParticipant]

Earthgirl

To answer your questions I will respond in the following order :
1. Yes Carbon (soot) can be produced by burning either Natural Gas or LPG gases BUT only where the flame tip impinges upon an object such as an imitation log object – this causes the characteristics of the combustion gases (carbon dioxide and water vapour) to change somewhat and will produce a carbon heavy result. When this effect happens it is a dang good bet that carbon monoxide will be produced in the burning of the fuel. Carbon Dioxide is a non smelling poisionous gas that is absorbed into the bloodstream and is not easily dissapated. Prolonged exposure will almost certainly cause serious illness and may lead to death. It is not something that folks should muck about with – have the appliance tested for combustion gases urgently.
Sooting (carbonisation) of the flame can also be caused by lack of servicing where the air slides into the burners have been blocked or restricted by the ingress of lint or other objects.
There are many of these unflued log sets in use by homeowners throughout the World but most are vented allbeit partially to the atmosphere to prevent the buildup of moisture (carbon dioxide and water vapour) which are the combustion gases from a correctly set up and burning gas appliance.
It is now mandatory down here for these type of appliances to be fitted with an oxygen depletion device as an integral part of the standing pilot light. Should an event such as insufficient oxygen for the burners correct combustion happen then the pilot will go out and shut down the appliance completely and will not allow the same to be operated again unitil there is sufficent free oxygen available for the pilot to burn again.
So in closing I suggest that 1. The appliance is fully serviced and set up again correctly to manufacturers specs, and 2. The some form of permanent ventilation be provided to enable the burner to remain burning correctly. and 3. Fit a vent to atmosphere to allow the exhaust gases to be vented to atmosphere.
Please note that these “log sets” are really only designed to be asthetic units and not the major source of room heating.
Hope this somewhat lengthy dissitation assists you.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

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