Olfaction, the sensing of chemical cues, is a key task for most animals. A variety of crustaceans, including marine crustaceans and insects, gather chemical cues by moving external chemosensory hair arrays through environmental fluids. These arrays come in a vast diversity of morphologies and interact with a large number of odorants. Many of these hair arrays are dense, providing a large odor-capture surface area to detect rare odorants. However, the outer hairs of a dense array shields inner hairs from fluid containing odorants. Does the density of the array help to detect rare/dilute odorant signals? And does the fluid or speed of movement matter in detection? We constructed a variety of different hair arrays using a computational fluid dynamics model, varying in hair number and arrangement and simulated odor capture in a range of fluid properties and odorant diffusion coefficients. We found differences between hair array configurations in terms of shear flow around hairs and the overall leakiness on the array, and these depend heavily on the Reynolds number of the array. Odor capture varied with each array, and more sensory surface area did not result in higher levels of odorant captured, but varied with odorant diffusion coefficient and specific configuration. These results could help to describe the performance of hair arrays with common versus rare target odorants.