Exploders can be distinguished from regular zombies by the greenish liquid and fire around their body. They spawn during regular rounds, and spawn at rounds after the first Host round.
When approached, the Exploder will, as its name indicates, explode in a manner similar to the Napalm Zombie from Call of Duty: Black Ops. The explosion deals small damage to nearby players but will one-hit kill nearby zombies. If the player does not kill an Exploder for a period of time, it will charge up and when killed the blast radius will be increased and possibly hurt or in rare cases down any player in the vicinity. If the player kills an Exploder, its explosion will not affect other players.
During a Security Dogs round, there is a small chance for a Security Dog to have the characteristics of an Exploder. When killed or approached too close, these dogs will also explode.