Question

why is the dispersion of gasses through long chimneys undesirable?

Answer 1

We will discuss the drawbacks of long chimneys from the point of air pollution and dispersion of gaseous pollutants.

Long chimneys do help in the dispersion of gases over a vast region but dispersion through long chimneys only reduces the concentration of the air pollutants at a particular source and doesn't reduce it as a whole.

In a broad manner, long chimneys only act as a method of dispersing the gaseous contaminants to a far off place rather than around the vicinity of the chimney. It, in no way helps in the reduction of the amount of gaseous discharge into the air. The only difference is that the effects of this gaseous discharge are observed at a far off place rather than at the source.

It has also been seen that the SO​​​​​2 emissions from long chimneys in one country lead to acid rains in the neighboring countries.