Consumers Report Magazine Says...

From Consumers Report Magazine January 2010:

Where There's Smoke: Four Myths About Chimneys

A wood-burning fireplace is the most inviting way to heat. Reduce the
risk of chimney problems by installing a chimney cap to keep out
rain, animals, and debris, and beware of these maintenance
misconceptions:

Myth: Unused chimneys don't need inspecting.
Reality: Cracks can develop and weaken the structure,
and obstructions like bird nests can build up. An annual inspection
allows you to fix small problems before they become big.

Myth: Focus on structural issues.
Reality: Blockages or a buildup of creosote can cause fires and
carbon-monoxide poisoning. Dirty chimneys cause most chimney and
flue fires, according to the National Fire Protection Association.

Myth: Expect to pay $40 for a basic inspection and cleaning.
Reality: Fraud alert! Once in your home, a cheap sweep is likely to
say there's damage that will cost thousands to fix. A basic
inspection and sweeping usually costs $150 to $300, the nonprofit
Chimney Safety Institute of America says.

Myth: Some good sweeps take 10 minutes.
Reality: Even a basic, level-1 inspection and sweeping takes 60 to
90 minutes. The sweep should ask about past problems. He'll turn off
fuel-burning appliances that vent into any of the chimney's flues and
will place drop cloths in the work area. He'll inspect the chimney
and flashing. He'll clean the chimney and tidy the firebox, noting
problems. A level-2 inspection, $225 to $450 and 90 to 120 minutes,
is apt when the chimney has been structurally changed. Level 3 could
be costlier and might even involve demolition.