We use them in both fireplaces. I think they say to burn one in every sixtieth fire. I hope they work, but we don't really have practical access to our chimneys to inspect them.

Merry Christmas

Have you tried shooting a picture "in the blind" without seeing your subject. This has worked well to document my cleaning before and after and the need almost yearly. I do have it fairly easy to get good Pics since I only have 60" of 14" inside dia pipe. I have access to from the roof with it�s cap off. I basically shoot multiple pics from inside the firebox up the chimney and inside the firebox that is about 6� high inside. I can extend my body inside the bottom of the firebox but that is not comfortable compared to blind shots that have worked on a 2 of 5 being good defining shots.

My cleaning is with an extended wire brush vs a log which I plan to try and document with before and after pics. Since the mid 70s I h/n seen what I felt was creosote vs soot that easily sweeps out. I had planned to try to burn what I am calling soot plus I felt if it were creosote it would burn in the firebox vs collecting "Correct"? loger

Please excuse me if this is a double post due to not seeing the 1st over a hr later.

The old timers used to use a white chicken and a black chicken to clean and check their chimneys!
First, they'd send down through the chimney, a black chicken, with a rope tied to its legs. They'd then pull it up and untie it, then send down a white chicken, and pull it up, to see if they needed to send down another black chicken!
My Great Grand-paw told me that method worked quite well! He said it made the chickens testy, but didn't harm them, and it got the chimney clean! rj ;0)

Just have it professianlly cleaned once per season.