Welcome to Just Answer.
Sorry to hear about your problem.
This is a typical problem with the ventless fireplaces. The only thing you can do is clean the slate and hope that you do not start seeing soot everywhere else. You could have the retailer that sold it to you come out and inspect that it is burning the propane correctly. More importantly, MAKE SURE that you have carbon monoxide detectors installed-- this is a big problem as well. Click here to learn more.
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Best of Luck, Brian
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