Hazmat Infected

The Hazmat-suited Infected was the first Uncommon Common to be announced and appear in the Left 4 Dead 2 campaign, The Parish. Valve has also indicated that they may appear in the Dead Center campaign as well. Players will occasionally come across Common Infected wearing a Hazmat Suit, which was likely being worn prior to the person being infected. It has also been said that when they're killed they drop a bile bomb.

Though not as numerous as normal Common Infected, they share the same health, abilities and weaknesses. However, due to their Hazmat Suits, they are immune to fire in all forms. This includes:

* Incendiary Ammo (this type of ammo does kill them but not by setting them on fire) * Static Fire (e.g. Burning barrels) * Gas Canisters * Molotov Cocktails

According to Chet, there is going to be an area that is "literally filled with them". This may be the CEDA strongpoint that was mentioned that The Survivors must breach. A group of them make an appearance in the zombie survival guide trailer walking through flames while the infected around them were engulfed by the fire.

Trivia

 * They was the first uncommon infected to be conceived.