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A stack is a type of chimney used to exhaust gases into the outside air. Stacks work by releasing gases high and fast enough so that odour emissions are widely dispersed. This means odours are less likely to impact on nearby sensitive receptors. Gas emissions may require treatment with other odour prevention methods before they are exhausted through a stack.
How stack height results in good odour dispersion (top), and poor odour dispersion (bottom):
Type of control
When you would use this
If your business generates odorous gases, then a stack is a recommended way to release these treated gases into the outside air.
Suitable for: any gaseous odours.
Industries that would use this: any industry that treats or produces odorous gases could benefit from a stack.
Details and considerations
While a stack is a very useful piece of engineering, there are several considerations to keep in mind when deciding if a stack is right for you:
- Stacks do not actually eliminate any odour, they simply disperse it widely enough to dilute the odour so that it is less detectable, or not detectable at all, by sensitive receptors. When installing a stack, coupling it with other odour prevention methods is recommended.
- There are certain requirements when building and installing a stack to ensure it fulfils its purpose. Getting this right will mean consulting a contractor or engineer for design and/or installation.
- Ensure your stack/s adhere to council planning permissions, especially for smaller businesses.
For effective odour reduction, it is important to ensure your stack meets the following requirements:
- It is structurally sound, well designed and properly installed. You may need to engage appropriate contractors for this.
- Stack design should consider the local meteorological conditions.
- Depending on your operation, you may need more than one stack.
- A contractor can undertake air modelling to ensure optimum design to meet the State Environment Protection Policy (Air Quality Management) design criteria.
- The exhaust exits your site from a vertical, open topped, stack.
- The stack is a minimum of 3 metres taller than any other structure within a 20 metre radius of the stack (this is important for odour dispersion).
- The stack emits exhaust at a speed of at least 10 metres per second (this is important for odour dispersion). Achieving this will require the installation of a stack with the correct diameter and fan running at the correct speed.
For more comprehensive information on stacks see relevant Australian Standards:
- Australian Standard AS4323: Stationary source emissions selection of sampling positions
This page was copied from EPA's old website. It was last updated on 18 June 2019.
Reviewed 27 July 2021