This summer has been a bad one for wildfires and the resultant smoke filling the city, today is no exception and the city is blanketed in a thick cloud of smoke. Thick enough that, standing on my balcony, I can barely see buildings in my neighbourhood through the gloom. I've taken to habitually checking the smoke forecast before going outside and doing anything. In the process it got me thinking about dispersion models and how they work. Beyond forecasting the forest fire smoke, they are used throughout industry to predict where emissions from vents and stacks will go, and also in modeling emergency scenarios (if there is an uncontrolled release of some kind, where will it go?).