cut the cheese

cut the cheese (to release intestinal gas) — испортить воздух; портить воздух

Example: Hey, who cut the cheese?

Some more euphemisms for farting

"Oops, I stepped on a frog!"
"Oops, there must be barking spiders here!
"Dude, did you have to let one rip in the elevator? Why didn’t you wait till we got out?"
"Did you let one go?" (said accusingly)

Used humorously when you’ve been caught in the act in some social situation (esp. if it's loud)

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Just for completeness, the idea of cutting the cheese must derive from the fact that the rind on some cheese reduces the odour, so that the cheese (brie, camambert or suchlike), once cut is much smellier.