Smoke Bomb

Smoke Bomb or Smoke Pellets are an item used by Batman, Robin, Nightwing, and Batgirl to escape from armed henchmen when under fire or to distract enemies.

Their first appearance was in Batman: Arkham City where Batman first used them in the Church and Medical Center against four of the Joker's Henchmen.

Initiation
Bruce Wayne utilized a version of that both as a similar method to his later days as Batman, and as a stun mechanism in combat, both known as the Kijuki Bomb. That variant created purple smoke.

Batman: Arkham Origins
The Smoke Bomb was used by Batman even in his early years as a vigilante, and was made to escape extremely dangerous situations, take out criminals in the smoke, cause confusion, and scare criminals.

When playing as Deathstroke, he had his own equivalent to Batman's Smoke Pellets. Deathstroke tossed down unstable stun grenades that covered his enemies in a jacket of smoke.

Batgirl: A Matter of Family
Batgirl used Smoke Bombs to when she went to rescue her father, Commissioner Gordon from the Joker at Seagate Amusement Park in predator.

Batman: Arkham City
The Smoke Bomb was used to escape from Armed Henchmen or to distract enemies and beat them up.

Batman: Arkham Knight
The Smoke Bombs worked like they did in the previous games, and had two WayneTech upgrades available for them: Smoke volume and duration. However, Robin didn't use them anymore. Harley Quinn also had a variant of that gadget, which released laughing gas instead of smoke. It worked identically to the one that Batman used, but enemies laughed when they were trapped in the cloud.

Trivia

 * During Batman: Arkham Origins, when Batman was battling Deathstroke, Deathstroke threw a flash bang at Batman, which deafened and blinded him, as that was used similar to Batman's Smoke Pellet. However, as you played as Deathstroke, you could only use 3 Neural Pellets.
 * In Arkham Origins, only one Smoke Bomb could be used, while in Arkham City, the player could use infinite amounts of Smoke Bombs, though there was a delay.
 * In Arkham Origins, there were two upgrades for the Smoke Bombs: increased smoke volume and increased smoke duration. Using those two upgrades and the Quickfire Glue Grenade- Takedown predator rooms could be completed extremely quickly. Enemies that used thermal goggles should be the first priority, if one tried to use that strategy.