Exhaust Dispersion and Design

Managing building air quality to enhance occupants’ experience and improve building and equipment performance

The effect of air quality on and near a building can make or break a project. When it’s understood and managed properly, nobody notices. When it’s unanticipated or unresolved, everybody notices—and complains.

Mechanical equipment on rooftop

To create a high-performing building, you have to know how air quality can affect your design. For example, will the building exhaust recirculate right back into the building, causing occupants to breathe unhealthy air? Will it contaminate the daycare center or operating room? Will exhaust affect the performance of equipment? Will the plume freeze on the façade?

Assessing and mitigating building air quality issues can be complex. Wind flow around buildings is the key. Exhaust travels with the wind, and wind is invisible. As a result, sometimes exhaust ends up where you least expect it, like at an air intake opposite the direction of the wind. Seemingly small design choices, such as architectural features or equipment placement, may have unexpectedly broad effects on wind flow patterns, either positive or negative. It takes a specialist eye to see the unseen and to bring practical solutions to this often complicated issue.

Our service

We understand that there are many moving parts in a design process, and we partner with you and your team to navigate these complex issues. We can help you solve an existing air quality problem, proactively design a retrofit or renovation, or avoid issues in new construction.

Whether you have a simple question about placement (“Is the emergency generator too close to the air supply?”) or broader concerns about an unusual building geometry, we help you zero in on the critical issues in your design. Then we deliver advice and creative solutions specific to your concerns and design goals. We are very familiar with air quality issues specific to many sectors, including healthcare, laboratory/research, manufacturing, commercial, institutional, and residential projects, data centers, and transportation facilities. We already speak your language.

Our key service is providing practical design advice. First we model how exhaust disperses in the presence of buildings and structures, and then we predict where it will go. We build a clear picture of how the wind interacts with these structures to affect the dispersal and transport of pollutants and odors. We predict whether the exhaust will re-enter a building (often called re-entrainment), affect a neighbor or outdoor area, affect equipment, or affect other parts of the building or its systems. To do this, we leverage our experience, supported by the use of numerical or physical models—or both if needed.

RWDI has deep, long-standing, and company-wide expertise in wind flows around buildings, microclimate effects, ventilation, and computational fluid dynamics modeling. We draw collaboratively on this expertise throughout the consultation, from choosing the right modeling strategy for your needs to interpreting the results in the larger context of your whole project so that we can help you design healthier, higher performing spaces.

Sector Challenges


  • Create an environment that is more supportive of healing
  • Protect sensitive patient spaces (operating theater, maternity, NICU, ICU, etc.)


  • Prevent re-entry of chemical exhaust from fume hoods
  • Save energy and money by matching exhaust fan flow rates to actual localized risk
  • Protect sensitive specialty labs from outdoor contaminants


  • Maximize value to tenants by creating comfortable, healthy, odor-free interior spaces


  • Avoid effects on the health and comfort of residents
  • Avoid complaints about odor (typically arising from diesel sources and kitchens)

Data Centers

  • Save money on critical cooling by preventing re-entry of excessive heat
  • Reduce the impact of diesel odor from emergency generators

Transportation Centers

  • Protect travelers in the event of a fire (e.g., subway, train) by allowing for safe egress
  • Improve travelers’ experience by preventing exposure to vehicle exhaust in concourse or pedestrian areas