I know, of course, that you can’t just up and burn wood in a gas fireplace with no adequate flu or ventilation. My REAL question, I guess, is whether a fireplace can burn both—the danger being the gas supply, not the ventilation. I’d plan and design for a real wood or coal grate fire but use gas and inserts but would still like to burn the real thing every now and then.

It would be a bad idea to burn wood in a gas fireplace. Wood is inherently dirty. Particulates are lareg comapred to the almost none in a gas furnace. Gas is metered by smal orifices. along a series of tubes. Lets say your fireplace was a reasonably large 32,000 BTU per hour unit with a total of 32 nozzles to distribute the heat. That means each nozzle is flowing 1000 BTU/hour. Using the handy chart below you can see the orifice needs to be about 0.020 inch or 0.5 mm. Those are small holes that can easily be clogged by creosote and or ash. You would have to clean them out every time you burned wood.

Gas orifice size to BTU flow. Chart

Coal burns much hotter than wood and can damage certain steels. The stove would have to be built specifically to take the high heat. Most are not.

While I absolutely trust @LuckyGuy’s expertise, my father, who had built LNG plants and refineries, had a gas feed installed in his fireplace at his vacation home. And we used it for years without any problem.i believe it was designed to not suffer the issues that were mentioned regarding particulates and creosote.

Gas, since it burns so cleanly and well – efficiently and completely, that is, at the point of combustion – does not require a heat-protected flue (not “flu”). If you look at the flue from a modern gas furnace for home use it will probably have a PVC flue and no insulation.

You can’t do that for wood, oil or coal! Those fuels do not have the same combustion characteristics (and fuel oil and coal in particular have such high heating values to begin with) that they require either masonry chimneys or insulated metal flues and thimbles (the intersection between the flue and the combustible wall or roof structure) in order to safely vent the very hot exhaust gases to outside atmosphere.

The flue from a gas log burner or other gas appliance also doesn’t have the volumetric capacity to handle more than a tiny solid fuel flame, in any case. You’d end up smoking up the entire room and not exiting enough of the flue gases, and that adds the high risk of carbon monoxide poisoning.

Don’t even consider burning other fuels – not even paper! – in a gas log fireplace or burner. (Aside from the flue issues, coal, wood, paper and other solid materials have ash considerations that a gas burner does not need to be designed for.)

If you burn other fuels than the burner is specifically designed for you risk the lives and health of the building occupants, as well as the risk of burning down the structure.

@zenvelo I’d love to know how your father diid it. Do you remember what the distribution tubes looked like was there only one with only a few holes? Or!!! Did he make the tubes easily removable so He could burn wood without having to clean the gas portion. Did he have a nice neat rack on the side of the fireplace to hold the tubes. .
also what kind of a flue. did he use. Fireplace is usually 6 or 8 inch. Gas is small 3” and some of the new ones are even ventless!
A large flue wastes heat by drawing warm heated air up and out of the house. Did he have a tricky damper that moderated that somehow.?
There are so many ways it could go wrong. If you remember the experience fondly he was a very clever guy. :-)

You can but you probably shouldn’t.

I think what @zenvelo is saying is the reverse of the OP: putting gas into an existing “fireplace” (as that term is commonly understood to mean a combustion area for wood, paper and other solid fuels) is no problem. It’s analogous to being able to put your bicycle into your garage; it fits just fine, with plenty of room left over. But you can’t put your car into a bicycle rack.

I am the Original Poster— I like Coal and Wood Burning fireplaces and would be glad to go to the full expense of a fully functional coal or wood fireplace (two coal and one wood burning). But I’d like to run gas most of the time as a regular heat source, as those who use regular gas heaters do.

There is a type of coal fireplace that was standardized in London in the 1880s and were built even here in the Americas until maybe the 1930s. Components are still produced today in England.

In the Americas from the 1920s onward, many of these were retrofitted with mundane gas heaters, which were relatively maintenance free and ran all the time. In recent years, fake but authentic looking coal and coal grates have been produced that burn gas. They look like a real coal fire—and if you’ve never seen one you have no idea how magical they look. In some ways like something in the northern U.K. or Ireland from the mid 1800s but in some ways like something right out of the Arabian Knights.

Someone else told me that if I was going to do this, burn real coal in it because there is nothing quite like a real coal fire. I’d like to supplement my heating with gas fireplaces but wonder if burning real coal occasionally would be doable,

As far as gas logs, virtually everyone knows the pleasure of a real wood fire. The hiss and the noise of moisture heating in the logs, the pop and crackle—the smell of a wood fire—and eventually the cherry red of a hot, dying fire—a gas log fire only temporarily gives the illusion but can be run all the time. Some times it would be nice to burn the real thing.

Its worth the expense to have the real thing(s) but would like the convenience of burning gas in ordinary time.

@Yellowdog Are you going to put a scrubber on your chimney? There are negative health consequences of living close to a coal or wood furnace.

Gas is an awful lot cleaner, so good on you for that.

Sounds better and better all the time. Thanks.

No.