That is a very good point, I was reading about poop on wikipedia and it does state that scat is produced which smells as to make us steer clear of the stuff as in contains sickness inducing bacteria. However, that does not explain why we naturally ,as humans, actually enjoy our own fart smells otherwise why would we take a sniffter of the gas if we do a fart under the duvet whilst in bed?
I believe in this case HFT stands for Human Fart Toxic and the regulator as mentioned relates to blow off valve