Ernie; The stove featured in the article found here: http://www.finehomebuilding.com/how-to-articles/kang-masonry-stove.aspx?ac=ts&ra=fp
was built by me in Missoula, Montana, in 1986. As you can see, the k'ang had a fairly large secondary burn chamber, about 40 feet of horizontal flue separated by firebrick walls and a cement block/clay liner, 8x12 chimney that stood in the corner of the room and was about 15 ft. in height. Flue runs were nine inches by approximately fifteen inches tall. Eventually, the firebox was fitted with an airtight steel door. As reported above, the stove burned vigorously, producing little smoke and no creosote. Primary and secondary pre-heated air was supplied through the door arrangement. Adding the door made the stove burn hotter and cleaner, as it offered control over excess air rushing through the system, and it allowed for some pre-heating of combustion air.
Cleanliness was never a problem, and it ate like a bird. One problem that did arise was perplexing. After a string of bad-air days, when the stove was cold, closing the door on a vigorously burning fire caused asphyxiation, and smoke problems. After repeated attempts, I finally reasoned that the bricks inside the stove, (probably 400 or so), were so cold they were absorbing all the heat from the flue gas before it got to the chimney. If the flue gas didn't rise up the chimney, fresh air would not be pulled in through the door frame. So, to solve the problem, I began burning the first fire after cold snaps with the door open. Problem solved.
Clean-out door at chimney-base offers a simple way to remedy any back-draft problems. If the stove is cold, a small wad of newspaper, or a weed burner, will easily and quickly reverse the flow. Typically what came up the chimney was clean, moist exhaust cool enough to put your face in, and a little fly ash.