Effect Duration 90 Seconds Combat Training, Fire Training , First Aid Training,  Gender Reveals Additional Information Pop the safety lid off the top then pull the ring out of the side and then before your very eyes a blanket of yellow smoke will appear.   Blue Further Information To function the smoke grenade simply pull the ring to the side. What follows is 90 seconds of brilliantly colour, non-toxic smoke. Smoke is delivered from a single vent at the top of the grenade. Blue Dimensions Smoke grenades do not require any licenses to use, however a license would be required to resell these grenades.