The smoke bomb appears to be made from either a burlap sack or brown paper bag full of sugar and explosives. It does not inflict any kind of damage. Instead, if human enemies are within its blast radius, they will be stunned. Also, it can be used to assist an escape from enemies in two different ways.
First, the smoke bomb can assist in escape from human enemies by blocking their line of sight. Second, if Infected are within a smoke bomb's explosion radius, then it will prevent the use of echolocation by Clickers.
In the single player campaign, Joel and Ellie can use a smoke bomb when overwhelmed by enemies, providing a means of escape. Human enemies will hesitate to attack Joel since they cannot see him. This works when the smoke bomb is still in effect and Joel is hiding in the smoke. The player can then use the smoke as cover to launch an assault, which can make combat easier. Joel can be stunned by the bomb if he stands too close to it. Training Manuals can be used to upgrade the smoke bomb, which can not only allow the smoke to stay longer, but also increase the bomb's explosion radius.
They are very handy when Joel encounters the Hunter's Humvee in Pittsburgh as one thrown close to the vehicle will cause the gunner to hesitate before firing, giving the player a chance to get to cover. and smoke bombs are also very useful when you encounter the military sniper in the suburbs and also in the Firefly lab when faced with several Assault Rifle equipped Fireflies.
Against the InfectedEdit
On 1 July 2014, Naughty Dog Game Designer Doug Holder stated "a smoke bomb cloud makes Infected unable to hear you", confirmed by Naughty Dog Game Designer Bruce Straley who stated "I was trying to balance the smoke bombs with the clickers"
Regardless, the Infected are drawn to the smoke created by the bomb and are indeed unable to hear or see the Player although they do hear gun shots and other noises despite this. In particular, they appear to freeze in place if caught in its direct blast radius. The most ideal use of this is when the player is fleeing the Suburbs and has to stall time to escape.
Smoke bombs allow screening and stun enemies caught in the radius for roughly 2.5 seconds, allowing the user to shoot the victim, attack them hand-to-hand while they are blinded, or perform a shiv kill from any direction. However, the thrower can be stunned if caught in the blast, which can be remedied by using Bomb Expert 3. They can also be used as a diversion or means of escape; since the enemy is blinded by the smoke, they can't shoot accurately at the player.
The smoke bomb detonates a couple of seconds after being thrown. The time between throwing the bomb and detonation can be reduced through using Bomb Expert and its variants.
Smoke bombs are useful in conjunction with Hawkeye 2 or 3, as enemies are outlined in red when marked, practically nullifying the smoke's effects.
In Interrogation, hitting an opponent with a smoke bomb while they are interrogating a teammate will stop the interrogation. However, this will not officially count as an Interrogation Denied, and the player will not receive the parts for one.