GTA V: Throw BZ Gas into the air vent
Call up the weapon wheel and choose the BZ Gas Grenades. Cycle on through your grenade choices until you find it.
Now, follow the prompts to pull them out, aim your throw and let them loose. You need to get them in the middle of the surrounded vent area. Prior, there was a yellow circle that was glowing. That is your target. Just line up the targeting with the circle and throw.