The gas bomb is constructed from a sensor module rigged to a pilot light that, when strapped to a fire extinguisher, creates an improvised explosive incendiary device. It is thrown a short distance when placed, instead of being dropped nearby like other mines. Like all other placed explosives, it cannot be used in V.A.T.S.
The weapon functions like other proximity mines when placed by the player, and will burst into a ball of fire and shrapnel, setting the target ablaze and causing explosive and fire damage. The explosive activates when a land-based target approaches within 4.6 feet and detonates in a 28-foot radius after a three second timer. The target's explosive skill (or lack thereof) can determine how long the countdown actually lasts.
The ghost people seekers that walk the villa use these explosive device frequently. Internally, ghost people use a separate version of the gas bomb that functions as a large, short ranged grenade; it detonates on a 2.5 second timer and does not require a target to enter any sort of proximity to the bomb.