fieldstone chimney? I would go to local stone dealer & explain what you would like to do - i think 1 gal of stone cleaner,use it diluted should do the job - i have not heard of using oven cleaner nor would i - you are right to be concerned about all the other materials this will be hitting - have dealer explain to you how to clean/use product carefully

Well, forget the slum lord bit. We have the same set up in our 1st floor kitchen (see photo) and the 2nd floor above it had a blocked opening. I seriously doubt anything nefarious. In our 1st floor kitchen the chimney was obviously used for the cooking stove. 2nd floor -who knows? But certain that it was for heating, and also certain that not every room received a fireplace ($$), -some just got a wood stove. Stranger is that you have (had) lath covering the chimney, which would be a fire hazard if a device was ducted there. But if one was once and later removed, one would think that this would have occurred after the period when wooden lath was used (given your house @ 1919).

@EricHeisel, that sounds fairly normal (although worth considering akamainegrower's suggestion too). Keep in mind: since you have a fireplace you vent through that chimney, you may need to ensure it gets inspected / looked at by a fireplace specialist (or that your masonry contractor has the proper qualifications). You wouldn't want to have that work done and then find out something else needs to be done to meet code/safety regs for venting your fireplace (like getting the structural work done and finding out later it now needs a liner). Your masonry contractor may know this all but check - the structural issues may be different from the fireplace/venting requirements. Of course it's possible your current chimney has a steel liner inside it now, too.

First, do no harm. We, too, have a very old house, a fireplace in every room. Some of them have been blocked so they are no longer functional, but integral to the design and credos the history of the house. We found a good chimney sweep to insect all of the fireplaces and chimneys. We developed a plan of action to make them both safe and functional. We bought the house because of the cooking fireplace in the kitchen so we knew even before we made an offer we would spend money to make that fireplace work properly. In the end, the chimney sweep lined five of our fireplaces with stainless liners, capped the chimneys so birds couldn’t drop in and sparks fly out, remortared some areas of the old fireboxes and, in one case, opened an 18” square area of plaster over the mantle to fix four bricks in one of the chimneys. Previously the house had ventless gas logs: research seemed to indicate safety issues related to asbestos and carbon monoxide so we knew they had to be replaced. Not only the safety of the house but the character of our house would be changed if we had not made these fireplaces useful. Our plumber removed the gas line to the 1817 kitchen fireplace because I only want to cook authentically with wood. Ham and bean soup will be simmering there today. We have new gas logs in the front and back parlors, the back parlor has a remote control because the tv is there so we use that room the most. The library has a gas starter so we can use wood and have the option of gas logs when we grow tired of hauling wood into that room. It is very tempting to do lots of changes when you first move. HGTV pushes the idea that you have to “put your stamp on your new house.” The opposite is actually true and most especially when you are lucky enough to have a really historic home. In everything we do, we try to honor the builder of our home. If he were to walk into our house today, I think he would be pleased. He would recognize his house and be comfortable here. Yes, we have heat and AC, indoor plumbing, and electricity, but we haven’t ripped out the plaster walls or replaced the 1903 windows in the oldest part of the house, or “updated” the floor plan to open concept. Visit other houses of the same era, read books about the time period so you know how the original owners lived. A thrill for us was discovering the gr-gr-gr-grandson of the original owner/builder of our home. Imagine sitting in our dining room with this man, laughing and talking, sharing a meal, and learning more about the family who lived and worked here in 1803! Priceless! Take your time and let the house tell you what it wants.