Pros and cons? The lady's house isn't set up for a woodburner so we're thinking about natural gas. Who has one?

Pros are no piping to the outside, and super efficiency...Cons are breathing the by-products of combustion, and coating windows, walls, and ceiling with those by-products as well.

They put out great heat and are very efficient. There is no smell unless you been cleaning or something and it mixes with the cleaning smells. As far as cons, they do put out a lot of moisture in the air. Especially if that’s the only heat source you are using. If you use it in combination with a furnace you can keep the moisture down.

How could a ventless fireplace even be possible. There must be some emissions.

every house I ever replaced the roof on that burnt a ventless fireplace had the sheeting rotted in the farthest corner from the heat source in that room.

I've used my ventless gas fireplace for over 20 years. I love it. It isnt my sole source of heat. My house gets so dry in the winter that Static electricity jumps from you fingers when you reach for something grounded. I havent noticed ANY moisture in the house, including no fog or moisture on my windows.
Waggler, Conceptually, A ventless Fireplace isnt much different than running a gas stove or oven.

Probably not any worse than a gas cook top or oven in the kitchen
Doug
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Thanks guys. It would not be the main source...only to warm my feet. They're cold all the time!

I'm guessing they are talking gas stoves...??? Had me confused too. When I think fireplace I think burning wood.
I was right there with you waggler.

If we are talking the blue flame ventless propane heaters, I heated a 500 sq ft shop exclusively with one and liked it. Never found any damage from high moisture levels, but this was also in a climate where relative humidity is pretty low in the Winter and not uncommon for people to run humidifiers just to put moisture in the air of their homes. I had a box fan running most of the time just to circulate the warm air.

That's what I was thinking, never heard of anything that doesn't burn wood called a fireplace. They must be talking about gas furnaces/heaters.

Must be a yuppie thing

It's basically a ventless space heater.