The reason of bad draught-out in a fireplace chimney can be concluded in insufficient height of a chimney over a roof, its wrong arrangement on a roof, insufficient width of a chimney, its overload caused by joining to it of several fireplaces, a leaky chimneyadjunction, the mount of two fireplaces against each other in one chimney, it may lead to smoke streams whirls.
Sometimes, trying to receive as much as possible heat, build too long chimney which have no enough slope for good draught and besides are quickly clogged by soot.
For quick draught check put the lighted candle in front of fireplace. If the flame does not deviate, it is mean the draught is weak; if the flame is promptly torn and dies away, draught too strong.
At normal draught the flame is quiet directed toward a fireplace.
If the reason of bad draught is concluded in a house location, for example, in lowland where air streams blow a smoke back into a chimney, draught can be improved by installing over pipe a chimney turbine nozzle which protects from undesirable air streams and creates soaking up effect.
Steel inclined nozzles work well until will rust. After that they become motionless, and draught again worsens. Therefore it is better to apply ceramic or fibrocement nozzles.