yes and it is possible. they also put off a lot of moisture and if the house is built tight all that moisture can result in mold. They also exhaust all the other combustion by-products into the house so it is a really bad idea if you have a tightly built house.
I really think that you should search the site for previous posts before you choose a ventless, (vent free) gas appliance. There have been many posts on them. Most are not favorable. Me personal experience agrees with that majority.
I've read a lot of these vent free threads. I'm surprised at the number of people that get so fired up (no pun intended) about it. I can appreciate everyone's concern for others safety and that is a good thing for everyone here to genuinly care for the safety of their customers. I am kind of split on the topic, but I think in some situations these vent free logs are perfectly fine. I have had a set for a couple of years now in a large masonry fireplace. This is a double sided fireplace that opens up into two separate large rooms. My house is older and not particularly air tight. I crack a window an inch or two when I operate the logs. I have the ceiling fans on low and reverse. I have a two top of the line CO detectors. I maintain the logs and keep them clean. These are great to really heat up the space quickly. I don't run these for long periods of time and our winters are pretty mild here. That is my experience with them.
Yes they are vent free logs in a large brick fireplace. The damper is actually broken so I couldn't shut it, but there is some sheetmetal underneath the damper to seal things up. It's not a 100% seal, but sealed for the most part. I suppose there is a small amount of products that can escape the voids.
We have many customers with vent free fireplaces. The one and only complaint I have ever heard from any of them is the commonly known fact the white scale and residue left from the moisture.
For all of these customers this fact is far over shadowed by the comfort, beauty and efficiency. Some even use them as the only source of heat for the entire home because they are tired of pellet and wood stoves.
If you have one installed make sure to have it cleaned and inspected on a yearly basis. If you do it should burn clean and consistantly for many years.
Installing a vent free log in a fireplace with an open damper is like burning money. It won't heat your home one bit and will not operate properly either.
It's not that they don't have any other heat source in their home. Most have electric baseboard or electric radiant in the ceiling. They just choose not to use it. I was just trying to prove a point that they are effective.
I live in a rural area and the local electric co-op has very stable prices. Propane prices have doubled here. It will be interesting to see how many start using electric heat.