Heating system service inspections of chimneys: Ask your heating service technician to check the chimney for signs of a problem when your heating system receives its annual service. This is especially critical for older chimneys which may use a "dead end" flue - one which terminates right at the top of the foundation, with no ash pit or clean out door lower than the chimney thimble which accepts the flue vent connector from your boiler or furnace. Dead end chimney flues can become blocked quickly by any debris falling down the chimney.

Chimney sweep inspection of flues: Ask your chimney sweep to clean fireplace flues regularly - the frequency depends in part on how much you use the chimney, what type of use is made (open fireplace, airtight woodstove, coal stove), and if burning wood, how green the burned wood may have been. High sap content makes lots of creosote and greatly increases the risk of a chimney fire.

Chim scan cameras to inspect chimney flues: Many professional chimney sweeps use a  camera, basically a   lens on a video camera, to examine the condition of the interior of the chimney flue. This is about the only way you can make a thorough examination of the chimney interior. When I shine even a bright light down a chimney from the top it's a bit like looking into an abyss of blackness.