Boiler flue
Boiler preventive measures
Have the boiler’s flue checked to make sure it is clean unblocked or partially collapsed.
If the boiler’s combustion gases cannot freely exit through the top of the flue, they may diffuse to apartments or other building spaces, creating a hazardous condition. Check flue tubes, over which hot water or steam passes, to ensure they are not leaking or clogged, as well as the insulation around the boiler piping.