human aerodynamic wake

According to the Annual Review of Fluid Mechanics Vol 38 page 92,

In still air, a buoyant flow of some tens of liters per second (L/s) rises from the body: the "human thermal plume". At a walking speed beyond about 0.2 m/s the plume gives way to the "human aerodynamic wake", as illustrated in Figure 2. Chemical traces originating as passive scalars on the body are found in these flows and can be sampled. Patterns of secreted proteins in the human plume or wake can be indicators of the early stages of a CBR attack.

Which means to say, if I want to conduct a terrorist attack at the canteen by farting, the damage will be worse if I walk around while I fart than to stand right next to a table and fart. The point is to have someone detect the chemical/biological attack.