Question: Do face masks protect against fart smell?
Short answer: No.
Long answer: The use of face coverings to protect against unpleasant air has a long history. A notable example is the case of plague doctors, who wore very strange masks like the one shown below to protect them from “putrid air”, which was thought to be the cause of disease.
Of course, the right kind of face covering can indeed be highly protective against the transmission of germs. Even very small pathogens, like viruses, tend to be on the order of 100 nanometers across, or 1×10-7 meters. This is similar to the pore size of N95 masks, which are used routinely in medical settings.
However, it does not follow that these masks protect against fart smell. The primary source of fart stink is hydrogen sulfide, a molecule to which the human nose is exquisitely sensitive. Each H2S molecule is about 360 picometers across, or 3.6×10-10 meters. So the molecules that give farts their characteristic smell are hundreds of times smaller than viruses. Using the supercomputing cluster at the ICEF, we have simulated the movement of a H2S molecule through a single pore of an N95 mask.
It is clear that these masks will do little to block the passage of H2S. In fact, given the size of an oxygen molecule (150 picometers), a mask that blocked hydrogen sulfide would probably make it difficult to breathe.
That said, our theoretical predictions have been inaccurate before, and we are an Experimental College. We therefore decided to put the theory to the test by farting through an N95 mask. This required an adaptation to our experimental system, the Bonaventure:
In this new system, farts must pass through the mask to reach the collection tube, which contains the air quality meter. Here are the data for a typical fart measured with this system:
As always, the lines correspond to fart smell detected at different depths from the source. Readers who are familiar with our previous measures of flatodynamics will see that there is nothing unusual about this fart. Both the magnitude and the time-course of fart smell are similar to what we typically observe in the absence of the mask. This suggests that our theoretical calculations are correct, and that masks can do nothing to block fart particles. Thus we maintain that the best way to avoid the smell of farts is to outrun them, which is easy to do.