Its share in the flue gases is only 5-10%.

它在烟气中所占的份额只有5-10%。

It can't be going out. - Well it is. There must be a block in the flue.

火怎么会熄呢。- 可就是熄了，烟道肯定堵住了。

As they blazed up they made a singing, harsh sound in the flue.

当它们燃烧时， 它们在烟道中发出刺耳的歌声。