info_logic_random allows mappers to randomize the effects of a trigger. info_logic_random behaves like a trigger_relay with just one twist – when triggered it will only fire its targets some percentage of the time. The chance key controls the probability of a successful activation, set it to a value between 0 and 1. The default probability is 0.5.
Technical note: info_logic_random entities do not work on the first frame of the game. The precache list must be deterministic to prevent save games bugs.