Air Emission Stack Height Calculator

Work out air emission stack height instantly with clear inputs, formula shown and shareable results.

About Air Emission Stack Height Calculator

Stack height is set by the most demanding of several criteria: at least 2.5 times the height of nearby buildings to escape their wake cavity, an empirical relationship based on sulphur dioxide emission rate, and whatever dispersion modelling shows is needed to meet ground level concentration limits.

Formulas

Good practice height

Height = 2.5 x nearby building height

Empirical SO2 height

Height (m) = 14 x (SO2 emission in kg/h)^0.3

Worked example

With the default values below, Air Emission Stack Height Calculator returns Recommended Stack Height of 42.34. Change any input above and every figure here is recalculated in your browser.

Inputs used

Pollutant Emission Rateminimum 0 g/s: 25 g/s
Nearby Building Heightminimum 0 m: 15 m
Sulphur Dioxide Emissionminimum 0 kg/h: 40 kg/h
Ground Level Concentration Limitminimum 0 microg/m3: 50 microg/m3

Results

Recommended Stack Height: 42.34
Good Practice Height: 37.50
Height From Sulphur Dioxide Formula: 42.34
Minimum Above Building Height: 18.00

Step by step

1Values used
2Good practice height
3Empirical SO2 height
4Recommended Stack Height= 42.34
5Good Practice Height= 37.50
6Height From Sulphur Dioxide Formula= 42.34
7Minimum Above Building Height= 18.00

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Stack height determination for permitting requires dispersion modelling to an approved methodology and regulator agreement. Empirical formulae are screening tools only.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Stack height determination for permitting requires dispersion modelling to an approved methodology and regulator agreement. Empirical formulae are screening tools only.

Frequently Asked Questions

Why 2.5 times building height?

Below that, the plume is drawn into the turbulent wake behind the building and brought rapidly to ground level, causing high local concentrations. Escaping the cavity is the first requirement of any stack design.

Is a taller stack always better?

It reduces local ground level concentration but increases the area affected and does not reduce total emissions. Regulators generally require abatement first and treat height as a residual dispersion measure.