From another article:

>Anyone within about 4 ft. of the fart will experience the effects within about 5 minutes. In contrast, as shown on the right, someone positioned opposite the fart path (i.e. in front of the farter), they will notice a slight change in air quality that dissipates after about 4 minutes.

>Considering only the trajectory on the left, we therefore arrive at an answer to the original question: The speed of an average fart is about 8 inches per minute. This is about twice as fast as a sloth can walk, but slow enough that one can easily outrun them.

>Of course, in our controlled experiments the farts were trapped in a tube, whereas in a natural setting they would be acted upon by air circulating in the environment. Air flow is therefore likely to be the primary determinant of the spread of farts. Farts are slow on their own, but if you really want to avoid the stink, the best strategy is avoid being downwind.