Zorflex

The fabric Zorflex is used in chemical warfare suits and is said to filter out odors 200 times stronger than the average human flatulence.
An English company is now manufacturing underware with the absorptive carbon cloth woven into the back panel.
"Shreddies" come in Men's boxer shorts for between $39 and $45 while woman's panties are about $31 to $34.
Caution - they do not block sound.

http://wtvr.com/2013/10/24/shreddies-fart-busting-underwear/

http://magazine.foxnews.com/at-home/new-sheddies-underwear-neutralizes-flatulence-odor-it-clears-room