CFD-Based Stack Height and Pollutant Dispersion Assessment for Design and Compliance
Client: University of Derby
Sector: Atmospheric Pollutant Dispersion
Challenge
As part of planned laboratory upgrades, the University of Derby required an assessment of the proposed fume stack configuration for B-Block. The upgrades included a significant increase in ventilation flow due to additional fume cupboards, raising concerns about whether the existing stack height would provide adequate dispersion of airborne pollutants.
Key priorities included:
- Preventing re-ingestion of exhaust gases at nearby air intakes and windows
- Managing exposure risk for building users and pedestrians
- Demonstrating compliance with UK health-based exposure standards
Solution
Navier carried out a computational fluid dynamics (CFD) based atmospheric dispersion study to evaluate plume behaviour under a range of wind conditions. The simulation accounted for:
- Local building wake effects and site topography
- Buoyancy-driven dispersion and atmospheric boundary layer behaviour
- A range of wind directions informed by site-specific wind rose data
To benchmark pollutant risk, a chemical survey was undertaken covering over 150 substances used within the laboratory. Based on hazard codes and evaporation characteristics, a shortlist of high-risk chemicals was developed. These were then assessed against EH40/2005 Workplace Exposure Limits, the UK’s official standard for occupational exposure thresholds.
To enable comparison across substances, the analysis used a normalised concentration approach (C/m) that evaluated the maximum pollutant concentration per unit of mass released — a method particularly suited to scenarios involving multiple volatile chemicals.
Outcomes
The CFD simulations identified wind directions in which exhaust plumes were recirculated or drawn downward toward sensitive receptors. Under these conditions, the dilution of certain high-risk substances was insufficient to meet conservative health thresholds.
However, the analysis also demonstrated that for the majority of routinely handled chemicals, the proposed 24-metre stack configuration provided sufficient dispersion. This provided the University with a clear basis for regulatory compliance, including justification against EH40/2005 limits.
The findings were used to support the project’s planning submission, ensuring that the proposed upgrades met environmental safety expectations. Where potential exceedance was identified, the study informed future design considerations such as stack height, efflux velocity, and discharge location.
This work formed part of the wider redevelopment of the B-Block laboratories, designed by Morrison Design for the University of Derby.
For more information on how Navier supports safe and compliant stack designs, visit our Stack Height and Pollutant Dispersion Analysis service.