In flight surgeon training in Texas we got to take a ride (and still need to
do so periodically) in the high altitude chamber, as do all current people
on flying status. Since gases expand as the ambient pressure decreases, we
were told to simply let it go when the urge arose.

Considering we were in Texas and eating a lot of Mexican food including
beans, this produced a lot of gas.

So, at high altitude, is it appropriate to say excuse me, ignore the
flatulence, or look at the guy in the next seat with disgust, as if he
(she)were the source? What is the proper etiquette with pilots of different
gender?

In fact, how does one use a relief tube with an FO of the other gender, or
vice versa? What is the correct response in these circumstances?

These questions address important aspects of flying that simply can not be
reproduced in the sim, so any help would be appreciated.