You can talk to any qualified chimney sweep, and they will point out the flaws with those soot cleaning products. I found one
Colorado Springs Chimney Sweep that was willing to take the time to explain why they are bad. I wasn't told they don't work, or do what they describe, but they do promote a false sense of security in their use. A chimney should be checked regardless of using soot cleaning products. A professional chimney sweep will sweep and examine your fireplace flue to make sure it is in good condition.
Concerned that I'm regurgitating information from a Colorado Chimney Sweep just trying to make a buck? Look at the chimney sweep logs, or stick, and you will find a warning about how they do not substitute yearly examinations of the fireplace and flue by a professional chimney sweep.
Be careful,
tom
For further information contact:
http://www.dr-soot.com/