The portable wind tunnel is one of the devices used to estimate the emission rate of odours from area sources. It has been conceived to provide better representation of the atmospheric boundary layer than the other device largely used for this purpose, namely the dynamic flux chamber. Ideally, the flow profile inside the wind tunnel would be close to a fully developed turbulent boundary layer, leading to better predictions of emission rates. However, its aerodynamic performance is still cause of discussion and clearly motivates further investigation. In the present paper, we use computational fluid dynamics to evaluate the flow inside of a portable wind tunnel and to discuss the necessary changes in geometrical configuration to reach the expected behaviour for such a device. The flow inside the main section of the device - where the incoming air comes in contact with the emitting surface – showed to be quite complex and not as well-behaved as expected. We propose and test other configurations for the device, aiming a scenario closer to the atmospheric boundary layer from an aerodynamic perspective. The alternatives considered include changes in the inlet section of the portable wind tunnel and present reasonable improvements for the velocity distribution, suggesting that small geometry modifications can lead to better aerodynamics.