[header] How to act like you didn't fart [title] Don't react to it. [step] This is rule number 1. The surest way to let everyone know it was you is to immediately look worried or ashamed. 
If you're around others and one gets loose, don't overreact-in fact, don't react at all. This is the opposite of what most people do when they accidentally leak one, so a strong display of ignorance will point people's suspicions another way.