Minecraft wiki entry for Lava, associated text: Most entities take 4 damage every half-second while in contact with lava, and are set on fire. An entity/player in lava will also have its remainingFireTicks set to 300, setting it on fire for 15 seconds. This timer is reset to 300 every tick that the victim spends in lava, so it will only start counting down once the victim leaves the lava. Once the victim does exit the lava source, it will burn for just under 15 seconds, taking fire damage 14 times. This is due to the fact that for the first tick outside of lava, its remainingFireTicks decrease to 299, and entities take fire damage when remainingFireTicks is a multiple of 20 and greater than 0. If the victim touches water or rain falls on it, the fire is extinguished, but the lava continues to damage them directly.