Out of the stack ?

I was out getting a wheelbarrow load the other night and with no wind I noticed black flakes coming out of the stack . Would that be enough reason to pull pipe apart to the thimble and check for build-up?

could be some fly ash or impurities in the coal burning off.

have you Checked your draft with a gauge lately. That would be an indication of possible ash build up.

I don't have ready access to to a draft measuring device

There is a loaner program on here you can request the gauge to measure your stove accurately.

If you are burning bituminous, you will get little pieces of soot floating out of the chimney at times... But if you haven't yet cleaned the chimney pipes yet this year, I would recommend it. At least to be able to say, with X amount of coal burnt, I had this amount of chimney soot and ash accumulation..
Then you can gauge when cleaning is needed.

Greg L

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you'll usually plateu at an inch1/2 or less of buildup, this is the point where the fluffy soot will simply begain to periodically blow out of the stack. don't be surprised to see an inch of buildup in your flue, but know that it generally won't buildup more than that in vertical runs.(unless you're burning wood too, then the sticky soot/creosote from woodsmoke will cause it to build indefinately); horizontal runs however will accumulate heavier fly ash as well as soot and thus still need to be checked monthly or so. don't worry about the soot outside, spring rains will wash it away.