from the Ontario
Fire Code ...
The Ontario Fire Code (O. Reg. 388/97) Part 2
Chimneys, flues, and
flue pipes
2.6.1.4
(1) Chimneys, flues, and flue pipes shall be
inspected
(a) annually,
(b) when any appliance is added to it, and
(c) after any chimney fire
(2) Chimneys, flues, and
pipes shall be repaired or replaced to eliminate any
structural deficiency (such as absence of a liner) or any
decay (such as cracking, settling, crumbling mortar,
distortion, advanced corrosion, separation of sections or
loose or broken supports)
(3) Chimneys, flues, and
flue pipes that constitute a fire hazard shall be repaired
or replaced in accordance with the Building Code.
2.6.1.5
Chimneys, flues, and flue pipes shall be cleaned as
often as necessary to keep them free from accumulation of
combustible deposits.