Molotov Cocktail

"Might wanna save this for later."

- Bill

"Grabbin' fire in a bottle, baby."

- Ellis

The Molotov Cocktail is a throwable weapon that engulfs an area with flames for approximately 15 to 17 seconds. The area of effect is quite large and spreads over time before self-extinguishing. The fire will burn all Infected that come into contact with it. Common Infected who run into the flames will burn to cinders, flailing wildly in the process. Special Infected, however, are able to withstand the heat; while they will burn to death unless they extinguish the fire, they can still attack Survivors. The Molotov Cocktail is dangerous in close combat because the splash damage and flames may cause the player and nearby teammates to lose health. While it is burning, it can ignite other combustibles such as the gas can, the propane tank, fireworks, the explosive barrel and the oxygen tank. Such items will continue burning even after being picked up, making them unsalvageable after ignition.

Survivors

 * When a Common Infected is on fire, neither the Infected itself or the fire on it will damage the Survivors, and water will not extinguish the flame. A burning Common Infected is generally considered dead (bots will not shoot them), but the fire can obstruct the player's sight and distract them.
 * Throwing a Molotov against a wall does not detonate it; it must hit the floor. This also applies to Special Infected; hitting one directly with a Molotov does not detonate it.
 * It is important in Versus and high campaign difficulties to conserve at least one Molotov for the Tank. Tanks have a lot of health, so they take a lot of damage from fire. They also can't extinguish themselves (nor can any other ignited Special Infected) unless there is a body of water nearby, ensuring constant, significant damage.
 * In Versus mode, Tanks will often actively avoid fire for this reason. The Survivors can take advantage of their hesitancy by blocking the path behind them with fire, giving them a chance to run ahead with only three Special Infected impeding them.
 * If the player runs far enough fast enough, they may be able to make the Tank die of frustration, allowing them to avoid a confrontation entirely.
 * The player can also block the path in front of them with fire to temporarily stop the Tank from attacking them. The 15-17 second burn time is more than long enough to heal, revive an incapacitated player, deal with lingering Common or Special infected, or run back to a more easily defensible area.
 * While it isn't extraordinarily difficult to defeat Tanks on lower difficulties, high difficulty Tanks and Versus Tanks can be a credible threat to even the most skilled teams. Successfully igniting a Tank can be the difference between victory and defeat in these scenarios.
 * A burning Tank will survive for 75 seconds on Easy difficulty, 80 seconds on Normal and Advanced, and 85 seconds on Expert.
 * Only in Left 4 Dead Campaign and Survival modes, setting the Tank on fire will increase his running speed, since he doesn't have much time to attack the Survivors.
 * Molotovs can bounce off obstacles and walls slightly, giving the player a chance to run away from the flame or throw it around a corner.
 * Generally, the player should refrain from throwing Molotovs in front of themselves, unless there is a Tank, a Horde, or the game is on Easy or Normal difficulty (in which fire does insignificant damage if one does not dawdle in the area of effect). If the area ahead is engulfed in fire and it isn't safe to run through it, the Survivors will be forced to wait it out, giving the Infected and Special Infected time to spawn.
 * Some Infected might take the opportunity to pull, lead, or carry a Survivor into or past the flames, cutting the victim off from their teammates and dealing extra damage over time (if they are stuck in the fire).
 * Also, be wary of Hunters attacking from the fire; they will be ignited, and therefore deal damage faster upon pouncing.
 * Do not hit teammates. If they are incapacitated inside a fire, it may be difficult to revive them without being incapacitated as well. On Expert difficulty, even Survivors with full health can die from the flames.
 * Setting a Witch on fire will gradually burn her health away and slow her movement (unlike the Bile Bomb, which the player should never use on a Witch unless far away), making her easier to kill.
 * Burning a Witch with the said weapon is rather risky, as it takes quite some time to kill, but in playing Left 4 Dead 2, burning the Witch then running with Adrenaline makes killing a Witch much easier.
 * Use fire with caution: setting fire to a Witch that is targeting a different survivor will cause her to shift her attack to the one who set her on fire.
 * It is not recommended to set a Wandering Witch on fire. Unlike the normal sitting version, the flames will increase her speed and allow her to catch up to you.
 * There's a trick to set a Witch on fire without her attacking. To do this, throw a Molotov to her and go idle before it hits the ground. If done correctly she will not be startled and will simply die without any risks to survivors. This trick is very useful on Expert and Realism mode where Witches are very dangerous. It's recommended to bind a key to go_away_from_keyboard since using the menu gives little time. This trick also works for gas cans.
 * Infected AI do not attempt to avoid fire in any way. If the player is aware of where a Horde is coming from, they throw the Molotov at a choke point between the Horde and their teammates. Try to throw the Molotov just as they reach the choke point in order to increase the likelihood of burning the entire Horde before the flames expire. Note that they may try to find a way around the fire, but it is not likely. Infected will travel in a straight line unless a static object is blocking the way. The fact that Infected seem to surround the Survivors is due to the AI counting other Infected as an obstacle to get around.
 * In Versus, players on the Infected team may avoid the fire and attack Survivors from the other side. Boomers may try to walk through the fire to ambush the Survivors and make himself a ticking bomb.
 * If the player throws a Molotov at the edge of a body of water (on a riverbank), it will still burn normally regardless of the water. However, the Molotov will not burn normally if thrown into the water.
 * There is at least one exception to this: Death Toll's first Crescendo Event in the storm drains. A Molotov thrown into the shallow water will burn as normal.
 * Also, despite the way water affected the Molotov in Left 4 Dead, it does not seem to affect them at all in Left 4 Dead 2. The many water-filled areas of Swamp Fever and Hard Rain can still support Molotov fire. Even the heavy downpours in the Hard Rain campaign cannot douse the flames. This is most likely for gameplay purposes, as if the water causes the flames to extinguish, a Tank/Horde will be free to kill the players easily without any more Molotovs being thrown at them.
 * However, since water will still extinguish a burning Tank or Special Infected, throwing a Molotov into water will be ineffective, as the Tank or Special Infected may simply extinguish itself in the surrounding water.
 * If a player is attacked by a pinning Infected (Jockey, Charger, Hunter, Smoker) in an area that the Survivors can't see (i.e. before a point of no return that the other Survivors have crossed), consider throwing a Molotov to ignite the attacking Infected. On lower difficulties, it is probable that the Survivor will be freed by the fire and still have enough health to reach their teammates without being incapacitated in the fire or by other Infected.
 * Such a strategy is viable for other grenades too, but the wide area of effect and instant activation of the Molotov makes it an especially prudent choice.
 * This strategy can also be performed to kill or weaken Special Infected that are hiding out of the Survivors' line of sight. Igniting a Tank that is hidden on a rooftop throwing rocks will force it to come down and attack the Survivors, giving them a chance to kill it.
 * In Scavenge Mode, this strategy can be used to destroy dropped gas cans that are out of reach and out of line of sight, allowing them to respawn in a reachable area.
 * Since the Molotov will not set off car alarms, a common strategy is to lob a Molotov at an alarmed car to kill any Smokers that would try to pull a Survivor towards the car (which will set off the car alarm).
 * A somewhat risky tactic, when the player is surrounded by Common Infected and needs to get away fast, is for the player to throw a Molotov at their feet and run. The fire will kill any Common Infected surrounding you. This is referred to as "Ninja-Toving" by some players. This should never be attempted on Expert and only on Advanced if the player has green health; on other difficulties, this only does about 5-8 damage to the player.
 * The player can clean a small room with Infected if they throw a Bile Bomb and then throw a Molotov where the bile bomb "explodes". Since the Infected don't avoid the fire, they will just walk into it. This method requires two players (one carrying the bile bomb and one carrying the Molotov) or can be done if there is both a bile bomb and a Molotov on the ground nearby.

Infected

 * Though it will eventually kill it, the Hunter does greater than normal damage when it is on fire. The bonus fire damage is only gained by lighting a Hunter on fire using a Molotov or gas can, not environmental fire (like in The Hotel).
 * Pouncing a Survivor who is standing in or walking through fire will redouble this bonus, providing extra damage both from the Hunter being on fire and from the fire around them. If the fire is not extinguished before the Hunter is killed, the Survivor will still be stuck in the fire while they stand up, further increasing the bonus damage they receive.
 * As a Boomer, the player can set themselves on fire to become a ticking time bomb. Run into Survivors to explode forcefully, since the Survivors can't safely push the Boomer away and shoot it without the risk of being exploded on. However, Boomers don't have very much health, so don't set it on fire too early.
 * If the Survivors run through the fire, attempt to explode while they are still in or near the flames. Survivors that are stumbled by the Boomer's death will remain in the fire longer than otherwise, increasing the damage they receive from it.
 * If playing as a Smoker, a great tactic is to drag a Survivor through the flames, causing extra damage and preventing others from rescuing them via shoving without taking damage. The fire can also obscure the Survivors' vision, making it more difficult for them to hit the player. However, take care, as they can still kill the player with their weapons.
 * In Versus, as a Tank, the Survivor team will usually immediately attempt to light the player on fire. The player must do their best to avoid the Molotov or gas cans they set up. If the player is stuck in front of a choke point, they will often have no choice but to run through and be lit. Either look for a way to extinguish the flames with water, or failing that, waste no time running at the Survivors and inflicting as much damage as possible.
 * It might be a good idea to wait for teammates to pin any Survivors that have Molotovs before attacking, delaying the threat of incendiary retribution by the Survivors. The player should consider pinning Survivors carrying Molotovs if they are an Infected supporting a Tank.
 * Similarly, if possible, the player can use the element of surprise to incapacitate any Survivors near them that are carrying Molotovs. A skilled Tank can land one initial hit on an unaware Survivor, then continue pounding them until they are incapacitated without any chance for them to use a Molotov.
 * Be careful, however, as this will probably force the Tank to stand in one position, leaving him vulnerable to other Survivors' attacks and other Molotovs or gas cans.
 * A good tactic for the Jockey is to try to ride a Survivor through the flames. This will cause flame damage and cut the lone Survivor off from the rest who will have to wait for the flames to stop in order to save their companion.
 * When playing as the Spitter, try to spit just in front of the flames where the Survivors are standing. The acid may cause them to panic and try to escape in any way possible, and this may cause some players to unintentionally jump into the flames, causing extra damage and confusion.
 * As the Charger, try to take players through the flames to the other side. This will hurt the player, but it hurts the Survivor as well and will leave them cut off from the rest of the group. Hitting any additional Survivors is a bonus, as if they land in the fire, they will receive extra damage before they are able to rescue their teammate, or even before they can stand up.
 * Try to predict where Survivors will throw Molotovs through the use of environment. If it appears that they will throw it in a certain location, move somewhere else.
 * Remember that if the player can pin, lead, carry or drag a Survivor out of sight while they are separated from their teammates by fire, they will be forced to either walk through the fire, causing them bonus damage, or wait for the fire to die down, giving the player a chance to deal extra damage.

Left 4 Dead 2
In Left 4 Dead 2, during the campaigns "Dead Center", "No Mercy", and "The Sacrifice", using a Molotov or incendiary ammo on the CEDA Worker Infected or Jimmy Gibbs Jr. will have no effect due to the hazmat suits or fireproof racing suit they are wearing.

Behind the Scenes
An early screenshot shows that the Molotov was gray and had a different-shaped top before becoming the final design. It was also intended to be a usable weapon in Valve 's other game, Half-Life 2, but was cut from that final version of the game before being introduced into Left 4 Dead.