If you turn on a flare and throw it, it will sometimes register it af is it is in your inventory. And it causes smoke and sparks coming from the char. this gives away position. The person controlling character isn't able to see it, it will only be seen by other players.
https://drive.google.com/open?id=0BwaZvTFN08wbQjNYTnFxZkd0NEk
Check the guy with the gas mask bug, the bug is happening at that moment.